Image decoding device and image coding device

ABSTRACT

A hierarchical moving image decoding device (1) includes a parameter set decoding section (12) that decodes a scaled reference layer offset syntax that is coded in a chroma pixel unit and a predicted image generation section (1442) that derives a scale based on a scaled reference layer offset which is a product of the scaled reference layer offset syntax and a luminance chroma size ratio of a target layer picture and generates a predicted image.

TECHNICAL FIELD

The present invention relates to an image decoding device decodinghierarchically coded data obtained by hierarchically coding an image andan image coding device generating hierarchically coded data byhierarchically coding an image.

BACKGROUND ART

As one piece of information transmitted with a communication system orinformation recorded in an accumulation device, there is an image or amoving image. In the related art, technologies for coding images areknown to transmit and accumulate such images (hereafter including movingimages).

As a moving image coding scheme, AVC (H.264/MPEG-4 Advanced VideoCoding) and High-Efficiency Video Coding (HEVC), which is a successioncodec, are known (see NPL 1).

In such a moving image coding scheme, normally, a predicted image isgenerated based on a local decoded image obtained by coding/decoding aninput image, and a predicted residual obtained by subtracting thepredicted image from an input image (original image) is coded. Aninter-frame prediction (inter-prediction) and intra-frame prediction(intra-prediction) are exemplified as a method of generating a predictedimage.

In intra-prediction, predicted images are sequentially generated in apicture based on a local decoded image in the same picture.

In inter-prediction, a predicted image is generated throughinter-picture motion compensation. The decoded picture used to generatea predicted image through inter-prediction is referred to as a referencepicture.

There are also known technologies for generating coded data from aplurality of moving images by dividing and coding the plurality ofmutually relevant moving images into layers (hierarchies) and thesetechnologies are referred to as hierarchical coding technologies. Codeddata generated by the hierarchical coding technologies is also referredto as hierarchical coded data.

As a representative hierarchical coding technology, scalable HEVC (SHVC)based on HEVC is known (see NPL 2).

In SHVC, spatial scalability, temporal scalability, and SNR scalabilityare supported. For example, in the case of the spatial scalability,moving images with a plurality of different resolutions are divided intolayers to be coded to generate hierarchical coded data. For example, animage obtained to have a desired resolution by performing down-samplingon an original image is coded as a lower layer. Next, inter-layerprediction is applied to remove redundancy between the layers, and thenthe original image is coded as a higher layer.

As another representative hierarchical coding technology, multi viewHEVC (MV-HEVC) which is based on HEVC is known. MV-HEVC supports viewscalability. In the view scalability, moving images corresponding to aplurality of different viewpoints (views) are divided into layers to becoded to generate hierarchical coded data. For example, a moving imagecorresponding to a viewpoint serving as a base (base view) is coded as alower layer. Next, inter-layer prediction is applied, and then movingimages corresponding to different viewpoints are coded as higher layers.

As inter-layer prediction of SHVC and MV-HEVC, there are inter-layerimage prediction and inter-layer motion prediction. In the inter-layerimage prediction, a predicted image is generated using a decoded imageof a lower layer. In the inter-layer motion prediction, a predictionvalue of motion information is derived using motion information of alower layer. A picture used for prediction in the inter-layer predictionis referred to as an inter-layer reference picture. A layer includingthe inter-layer reference picture is referred to as a reference layer.Hereinafter, a reference picture used for inter-prediction and areference picture used for inter-layer prediction are simplycollectively referred to as a reference picture.

The inter-layer image prediction includes a reference pixel positionderivation process of deriving a pixel position on a lower layer whichcorresponds to the position of a prediction target pixel on a higherlayer and a scale derivation process of deriving a scale correspondingto a magnification ratio in a scaling process applied to a picture of alower layer.

In SHVC and MV-HEVC, any of inter-prediction, intra-prediction, andinter-layer image prediction can be used to generate a predicted image.

As one application using SHVC and MV-HEVC, there is a video applicationconsidering a region of interest. For example, a video reproductionterminal normally reproduces a video of an entire region at a relativelylow resolution. In a case in which a part of a displayed video isdesignated as a region of interest by a viewer of a video reproductionterminal, the region of interest is displayed at a high resolution onthe reproduction terminal.

A video application considering the foregoing region of interest can berealized using a hierarchical coded data in which a video with arelative low resolution of an entire region is coded as coded data of alower layer and a video with a high resolution of a region of interestis coded as coded data of a higher layer. That is, in a case in which anentire region is reproduced, only coded data of the lower layer isdecoded and reproduced. In a case in which a video with a highresolution of a region of interest is reproduced, coded data of a higherlayer is added to the coded data of the lower layer to be transmitted.In this way, it is possible to realize the application in a transmissionband less than that in a case in which both of coded data for alow-resolution video and coded data for a high-resolution video aretransmitted. At this time, by extracting the coded data corresponding toa region including the region of interest from each of the higher layerand the lower layer and transmitting the coded data, it is possible tofurther suppress a transmission band.

In the foregoing video application considering a region of interest, apositional relation between pixels of the higher layer and pixels of thelower layer is changed in a case in which the coded data of the higherlayer and the lower layer including the region of interest is generated.As a result, there is a problem in that prediction accuracy deterioratesin a case in which a pixel value of the higher layer is predicted basedon a pixel value of the lower layer.

In SHVC (see NPL 2), a scaled reference layer offset is adopted as aparameter indicating a positional relation between pixels of a higherlayer and pixels of a lower layer. The scaled reference layer offset isa set of offsets indicating the position of a predetermined region on areference layer (for example, an entire reference layer picture) on ahigher layer which is a target layer.

NPL 3 discloses a method of realizing matching between reference pixelpositions (correspondence reference positions) or before and afterextraction of a scale by transmitting a reference layer offsetindicating the position of a region used for scale calculation on alower layer in addition to the above-described scaled reference layeroffset and by calculating a reference pixel position or a scale usingthe scaled reference layer offset and the reference layer offset even ina case in which partial data corresponding to a region of interest isextracted from hierarchical coded data.

CITATION LIST Non Patent Literature

NPL 1: “Recommendation H.265 (04/13)”, ITU-T (disclosed on Jun. 7,2013).

NPL 2: JCTVC-Q1008_v1 “Preliminary version of High efficiency videocoding (HEVC) scalable extension Draft 6”, Joint Collaborative Team onVideo Coding (JCT-VC) of ITU-T SG 16 WP 3 and ISO/IEC JTC 1/SC 29/WG 1117th Meeting: Valencia, ES, 27 Mar. to 4 Apr. 2014 (disclosed on Apr.15, 2014).

NPL 3: JCTVC-Q0159 “AHG 13: Sub-region extraction-position calculationand comparison of different approaches”, Joint Collaborative Team onVideo Coding (JCT-VC) of ITU-T SG 16 WP 3 and ISO/IEC JTC1/SC 29/WG 1117th Meeting: Valencia, ES, 27 Mar. to 4 Apr. 2014 (disclosed on Mar.18, 2014).

SUMMARY OF INVENTION Technical Problem

However, in the scaled reference layer offset and the reference layeroffset disclosed in NPL 2 and NPL 3, there is a problem in that acorrect value may not be set in a case in which the color format of apicture of a higher layer or a lower layer has a corresponding relationbetween a luminance pixel and a chroma pixel which is different from the4:2:0 color format. Therefore, a reference pixel position or a scalederived from the scaled reference layer offset and the reference layeroffset is different from an actual value in some cases. Accordingly,there is a problem in that a predicted image generated throughinter-layer prediction is inaccurate, and consequently a predictionresidual increases and a code amount of coded data thus increases.

The present invention is devised in view of the foregoing problems andan object of the present invention is to realize an image coding deviceand an image decoding device capable of setting an accurate value in ascaled reference layer offset or a reference layer offset in a case inwhich a picture with a different color format from a 4:2:0 color formatis a processing target of a higher layer or a lower layer, withoutincreasing a code amount of the scaled reference layer offset or thereference layer offset coded or decoded in a case in which a picturewith a 4:2:0 color format is a processing target.

Solution to Problem

In order to resolve the foregoing problems, an image decoding deviceaccording to the present invention decodes coded data that ishierarchically coded to restore a decoded picture of a higher layerwhich is a target layer. The image decoding device includes: a parameterset decoding section that decodes a parameter set; and a predicted imagegeneration section that generates a predicted image by inter-layerprediction with reference to decoded pixels of a reference layerpicture. The parameter set decoding section decodes a color format of atarget layer picture and derives a luminance chroma size ratio of atarget layer picture based on the color format. The parameter setdecoding section decodes a scaled reference layer offset syntax which iscoded in a chroma pixel unit of the target layer. The predicted imagegeneration section derives a scaled reference layer offset by a productof a value of the scaled reference layer offset syntax and the luminancechroma size ratio of the target layer picture, calculates a scale basedon the scaled reference layer offset, derives a correspondence referenceposition with reference to the scale, and performs the inter-layerprediction.

In order to resolve the foregoing problems, an image coding deviceaccording to the present invention generates coded data of a higherlayer which is a target layer from an input image. The image codingdevice includes: a parameter set coding section that codes a parameterset; and a predicted image generation section that generates a predictedimage by inter-layer prediction with reference to decoded pixels of areference layer picture. The parameter set coding section codes a colorformat of a target layer picture and derives a luminance chroma sizeratio of the target layer picture based on the color format. Theparameter set coding section codes a scaled reference layer offsetsyntax in a chroma pixel unit of the target layer. The predicted imagegeneration section derives a scaled reference layer offset by a productof a value of the scaled reference layer offset syntax and the luminancechroma size ratio of the target layer picture, calculates a scale basedon the scaled reference layer offset, derives a correspondence referenceposition with reference to the scale, and performs the inter-layerprediction.

Advantageous Effects of Invention

The image decoding device (image coding device) according to the presentinvention includes the parameter set decoding section (coding section)that decodes a parameter set and a predicted image generation sectionthat generates a predicted image through inter-layer prediction withreference to decoded pixels of a reference layer picture. The parameterset decoding section (coding section) decodes (codes) a scaled referencelayer offset syntax in a chroma pixel unit. The predicted imagegeneration section derives a scaled reference layer offset by a productof a value of the scaled reference layer offset syntax and the luminancechroma size ratio of the target layer, calculates a scale based on thescaled reference layer offset, derives a correspondence referenceposition with reference to the scale, and performs the inter-layerprediction.

Accordingly, in a case in which the color format of the target pictureis 4:2:0 or 4:2:2, the value of the reference layer offset syntax can bedecoded (coded) with a code with a less code amount than in a case inwhich the reference layer offset syntax is decoded in the luminancepixel unit. Further, in a case in which the color format of thereference picture is 4:4:4, the reference layer offset syntax can bedecoded (coded) with higher precision, that is, with luminance one-pixelprecision, more than in a case in which the reference layer offsetsyntax is decoded in a luminance two-pixel unit.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a flowchart illustrating a correspondence reference positionderivation process performed by a hierarchical moving image decodingdevice and a hierarchical moving image coding device according to anembodiment.

FIG. 2 is a diagram for describing the layer structure of hierarchicallycoded data according to the embodiment of the present invention, FIG.2(a) illustrates the side of a hierarchical moving image coding device,and FIG. 2(b) illustrates the side of the hierarchical moving imagedecoding device.

FIG. 3 is a diagram for describing the structure of the hierarchicallycoded data according to the embodiment of the present invention, FIG.3(a) illustrates a sequence layer that defines a sequence SEQ, FIG. 3(b)illustrates a picture layer that defines a picture PICT, FIG. 3(c)illustrates a slice layer that defines a slice S, FIG. 3(d) illustratesa CTU layer that defines a coding tree unit CTU, and FIG. 3(e)illustrates a CU layer that defines a coding unit (CU) included in thecoding tree unit CTU.

FIG. 4 is a functional block diagram illustrating a schematicconfiguration of the hierarchical moving image decoding device.

FIG. 5 is a functional block diagram exemplifying the configuration of abase decoding section included in the hierarchical moving image decodingdevice.

FIG. 6 is a table illustrating a relation among a color formatidentifier, a color format, a luminance chroma width ratio, and aluminance chroma height ratio.

FIG. 7 is a diagram exemplifying a relation between a display regionwhich is a partial region in a picture and display region positioninformation.

FIG. 8 is a diagram exemplifying a relation among a target layerpicture, a target layer correspondence region, a reference layerpicture, a reference layer correspondence region, and a scaled referencelayer offset.

FIG. 9 is a diagram illustrating a part of a syntax table referred to atthe time of decoding SPS extension and a portion related to a syntaxrelated to scaled reference layer offset information.

FIG. 10 is a diagram illustrating a part of a syntax table referred toat the time of decoding SPS extension and a portion related to a syntaxrelated to reference layer offset information.

FIG. 11 is a functional block diagram illustrating the configuration ofa slice decoding section included in the hierarchical moving imagedecoding device.

FIG. 12 is a functional block diagram illustrating a schematicconfiguration of a hierarchical moving image coding device according toan embodiment of the present invention.

FIG. 13 is a functional block diagram exemplifying the configuration ofa slice coding section included in the hierarchical moving image codingdevice.

FIG. 14 is a diagram illustrating the configuration of a transmissionapparatus on which the hierarchical moving image coding device ismounted and the configuration of a reception apparatus on which thehierarchical moving image decoding device is mounted, FIG. 14(a)illustrates the transmission apparatus on which the hierarchical movingimage coding device is mounted, and FIG. 14(b) illustrates the receptionapparatus on which the hierarchical moving image decoding device ismounted.

FIG. 15 is a diagram illustrating the configuration of a recordingapparatus on which the hierarchical moving image coding device ismounted and the configuration of a reproduction apparatus on which thehierarchical moving image decoding device is mounted, FIG. 15(a)illustrates the recording apparatus on which the hierarchical movingimage coding device is mounted, and FIG. 15(b) illustrates thereproduction apparatus on which the hierarchical moving image decodingdevice is mounted.

DESCRIPTION OF EMBODIMENTS

A hierarchical moving image decoding device 1 and a hierarchical movingimage coding device 2 according to an embodiment of the presentinvention will be described below with reference to FIGS. 1 to 15.

[Overview]

A hierarchical moving image decoding device (image decoding device) 1according to the embodiment decodes coded data subjected to hierarchicalcoding by a hierarchical moving image coding device (image codingdevice) 2. Hierarchical coding refers to a coding scheme ofhierarchically coding a moving image with low quality to a moving imagehaving high quality. Hierarchical coding is standardized in, forexample, SVC or SHVC. The quality of a moving image mentioned hereinbroadly means an element that influences on a moving image volumesubjectively and objectively. The quality of a moving image includes,for example, a “resolution”, a “frame rate”, “image quality”, and “pixelexpression precision”. Accordingly, a difference in the quality of amoving image refers to difference in, for example, “resolution” and thelike, but the present invention is not limited thereto. For example,even in the case of moving images quantized in different quantizationsteps (that is, the case of moving images coded with different codingnoise), the quality of a moving images can be said to be mutuallydifferent.

From the viewpoint of kinds of hierarchized information, hierarchycoding technologies are also sometimes classified into (1) spatialscalability, (2) temporal scalability, (3) signal-to-noise ratio (SNR)scalability, and (4) view scalability. Spatial scalability refers to atechnology for performing hierarchization in regard to the resolution orthe size of an image. Temporal scalability refers to a technology forperforming hierarchization in regard to a frame rate (the number offrames per unit time). SNR scalability refers to a technology forperforming hierarchization in regard to coding noise. The viewscalability refers to a technology for performing hierarchization inregard to a viewpoint position associated with each image.

Before the hierarchical moving image coding device 2 and thehierarchical moving image decoding device 1 according to the embodimentare described in detail, (1) a layer structure of hierarchically codeddata generated by the hierarchical moving image coding device 2 anddecoded by the hierarchical moving image decoding device 1 will bedescribed first, and (2) a specific example of a data structure adoptedin each layer will be described subsequently.

[Layer Structure of Hierarchically Coded Data]

Here, coding and decoding of hierarchically coded data will be describedbelow with reference to FIG. 2. FIG. 2 is a diagram schematicallyillustrating a case in which a moving image is hierarchicallycoded/decoded in three layers, a lower layer L3, an intermediate layerL2, and a higher layer L1. That is, in examples illustrated in (a) andFIG. 2(b), the higher layer L1 is the highest layer and the lower layerL3 is the lowest layer among the three layers.

Hereinafter, a decoded image corresponding to specific quality which canbe decoded from hierarchically coded data is referred to as a decodedimage of a specific layer (or a coded image corresponding to a specificlayer) (for example, a decoded image POUT#A of the higher layer L1).

FIG. 2(a) illustrates hierarchical moving image coding devices 2#A to2#C that hierarchically code input images PIN#A to PIN#C to generatepieces of coded data DATA#A to DATA#C, respectively. FIG. 2(b)illustrates hierarchical moving image decoding devices 1#A to 1#C thatdecode the pieces of coded data DATA#A to DATA#C hierarchically coded togenerate decoded images POUT#A to POUT#C, respectively.

First, the coding device side will be described with reference to FIG.2(a). The input images PIN#A, PIN#B, PIN#C input to the coding deviceside are the same as original images, but have different qualities(resolution, a frame rate, image quality, and the like) from theoriginal images. The quality of the images decreases in the order of theinput images PIN#A, PIN#B, and PIN#C.

The hierarchical moving image coding device 2#C of the lower layer L3codes the input image PIN#C of the lower layer L3 to generate the codeddata DATA#C of the lower layer L3. The coded data DATA#C includes basicinformation necessary to decode the decoded image POUT#C of the lowerlayer L3 (which is indicated by “C” in FIG. 2). Since the lower layer L3is the lowest layer, the coded data DATA#C of the lower layer L3 isreferred to as basic coded data.

The hierarchical moving image coding device 2#B of the intermediatelayer L2 codes the input image PIN#B of the intermediate layer L2 withreference to the coded data DATA#C of the lower layer to generate thecoded data DATA#B of the intermediate layer L2. The coded data DATA#B ofthe intermediate layer L2 includes not only basic information “C”included in the coded data DATA#C but also additional information (whichis indicated by “B” in FIG. 2) necessary to decode the decoded imagePOUT#B of the intermediate layer.

The hierarchical moving image coding device 2#A of the higher layer L1codes the input image PIN#A of the higher layer L1 with reference to thecoded data DATA#B of the intermediate layer L2 to generate the codeddata DATA#A of the higher layer L1. The coded data DATA#A of the higherlayer L1 includes not only the basic information “C” necessary to decodethe decoded image POUT#C of the lower layer L3 and the additionalinformation “B” necessary to decode the decoded image POUT#B of theintermediate layer L2 but also additional information (which isindicated by “A” in FIG. 2) necessary to decode the decoded image POUT#Aof the higher layer.

Thus, the coded data DATA#A of the higher layer L1 includes informationregarding the decoded images having a plurality of different qualities.

Next, the decoding device side will be described with reference to FIG.2(b). On the decoding device side, the decoding devices 1#A, 1#B, and1#C according to the layers, the higher layer L1, the intermediate layerL2, and the lower layer L3, decode the coded data DATA#A, DATA#B, andDATA#C and output the decoded images POUT#A, POUT#B, and POUT#C,respectively.

A moving image having specific quality can also be reproduced byextracting information regarding a part of upper hierarchically codeddata and decoding the extracted information in a specific lower decodingdevice.

For example, the hierarchical decoding device 1#B of the intermediatelayer L2 may extract information (that is, “B” and “C” included in thehierarchically coded data DATA#A) necessary to decode the decoded imagePOUT#B from the hierarchically coded data DATA#A of the higher layer L1and decode the decoded image POUT#B. In other words, on the decodingdevice side, the decoded images POUT#A, POUT#B, and POUT#C can bedecoded based on the information included in the hierarchically codeddata DATA#A of the higher layer L1.

The present invention is not limited to the foregoing hierarchicallycoded data of the three layers. The hierarchically coded data may becoded hierarchically in two layers or may be coded hierarchically in anumber of layers greater than three layers.

Some or all of the pieces of coded data regarding the decoded image of aspecific layer may be coded independently from the other layers, and thehierarchically coded data may be configured so that the information ofthe other layers is not referred to at the time of the decoding of thespecific layer. For example, in the example described above withreference to FIGS. 2(a) and 2(b), it has been described that “C” and “B”are referred to in the decoding of the decoded image POUT#B, but thepresent invention is not limited thereto. The hierarchically coded datamay be configured such that the decoded image POUT#B can be decodedusing only “B”. For example, a hierarchical moving image decoding devicecan be configured such that the hierarchical coded data formed from “B”and the decoded image POUT#C are used as inputs to decode the decodedimage POUT#B.

In a case in which the SNR scalability is realized, the hierarchicallycoded data can be generated so that the same original image is used asthe input images PIN#A, PIN#B, and PIN#C, and subsequently the decodedimages POUT#A, POUT#B, and POUT#C have different image qualities. Inthis case, the hierarchical moving image coding device of the lowerlayer generates the hierarchically coded data by quantizing a predictionresidual by using a larger quantization width than in the hierarchicalmoving image coding device of the higher layer.

In the present specification, the following terms will be defined tofacilitate the description. The following terms are used to describe thefollowing technical factors unless otherwise mentioned.

Higher layer: A layer located to be higher than a certain layer isreferred to as a higher layer. For example, higher layers of the lowerlayer L3 in FIG. 2 are the intermediate layer L2 and the higher layerL1. A decoded image of a higher layer refers to a decoded image havinghigher quality (for example, higher resolution, a higher frame rate, orhigher image quality).

Lower layer: A layer located lower than a certain layer is referred toas a lower layer. For example, lower layers of the higher layer L1 inFIG. 2 are the intermediate layer L2 and the lower layer L3. A decodedimage of a lower layer refers to a decoded image having lower quality.

Target layer: A target layer refers to a layer which is a decoding orcoding target. A decoded image corresponding to the target layer isreferred to as a target layer picture. A pixel that forms the targetlayer picture is referred to as a target layer pixel.

Reference layer: A specific lower layer referred to at the time ofdecoding a decoded image corresponding to the target layer is referredto as a reference layer. A decoded image corresponding to the referencelayer is referred to as a reference layer picture. A pixel that formsthe reference layer is referred to as a reference layer pixel.

In the example illustrated in FIGS. 2(a) and (b), reference layers ofthe higher layer L1 are the intermediate layer L2 and the lower layerL3. However, the present invention is not limited thereto, but thehierarchically coded data can also be configured such that none of thelower layers are referred to at the time of decoding the specific layer.For example, the hierarchically coded data can also be configured sothat the reference layer of the higher layer L1 is one of theintermediate layer L2 and the lower layer L3.

Base layer: A layer located lowest is referred to as a base layer. Adecoded image of the base layer is a decoded image having the lowestquality which can be decoded from the coded data and is referred to as abase decoded image. In other words, the base decoded image is a decodedimage corresponding to the lowest layer. Partially coded data of thehierarchically coded data necessary to decode the base decoded image isreferred to as base coded data. For example, the basic information “C”included in the hierarchically coded data DATA#A of the higher layer L1is the base coded data.

Enhancement layer: A layer higher than the base layer is referred to asan enhancement layer.

Layer identifier: A layer identifier is used to identify a layer and hasa one-to-one correspondence relation with a layer. The hierarchicallycoded data includes a hierarchical identifier used to select thepartially coded data necessary to decode the decoded image of a specificlayer. A subset of the hierarchically coded data associated with thelayer identifier corresponding to a specific layer is referred to as alayer notation.

In general, at the time of decoding the decoded image of a specificlayer, the layer notation of the specific layer and/or the layernotation corresponding to a lower layer of the specific layer can beused. That is, at the time of decoding the decoded image of a targetlayer, the layer notation of the target layer and/or the layer notationof one or more layers included in the lower layer of the target layercan be used.

Inter-layer prediction: Inter-layer prediction is prediction in whichsyntax element values of the target layer, coding parameters used todecode the target layer, or the like are predicted based on syntaxelement values included in the layer notation of a layer (referencelayer) that are different from the layer notation of the target layer,values derived from the syntax element values, and the decoded image.Inter-layer prediction in which information regarding motion predictionis predicted from information regarding the reference layer is alsosometimes referred to as motion information prediction. Inter-layerprediction in which prediction is performed from the decoded image ofthe lower layer is also sometimes referred to as inter-layer imageprediction (or inter-layer texture prediction). A layer used for theinter-layer prediction is, for example, a lower layer of the targetlayer. Prediction performed in the target layer without using thereference layer is also sometimes referred to as intra-layer prediction.

The foregoing terms are terms merely used to facilitate the description,and the foregoing technical factors may be expressed by other terms.

[Data Structure of Hierarchically Coded Data]

Hereinafter, a case in which HEVC and an extension scheme of HEVC areused as coding schemes of generating coded data of each layer will beexemplified. However, the present invention is not limited thereto, butthe coded data of each layer may be generated by a coding scheme such asMPEG-2 or H.264/AVC.

The lower layer and the higher layer may be coded according to differentcoding schemes. The coded data of each layer may be supplied to thehierarchical moving image decoding device 1 via mutually differenttransmission paths or may be supplied to the hierarchical moving imagedecoding device 1 via the same transmission path.

For example, in a case in which an ultra-high resolution image (a movingimage or 4K video data) is subjected to scalable coding in the baselayer and one enhancement layer to be transmitted, video data obtainedby performing downscaling and interlacing on the 4K video data may becoded in conformity to MPEG-2 or H.264/AVC and transmitted in the baselayer via a television broadcast network, and a 4K video (progressive)may be coded by HEVC and transmitted in the enhancement layer via theInternet.

(Base Layer)

FIG. 3 is a diagram exemplifying the data structure of the coded data(the hierarchically coded data DATA#C in the example of FIG. 2) whichcan be adopted in the base layer. The hierarchically coded data DATA#Cincludes, for example, a sequence and a plurality of pictures includedin the sequence.

The hierarchical structure of the data in the hierarchically coded dataDATA#C is illustrated in FIG. 3. FIGS. 3(a) to 3(e) are diagramsillustrating a sequence layer that defines a sequence SEQ, a picturelayer that defines a picture PICT, a slice layer that defines a slice S,a CTU layer that defines a coding tree unit (CTU), and a coding unit(CU) layer that defines a CU included in the coding tree unit CTU,respectively.

(Sequence Layer)

In the sequence layer, a set of data referred to by the hierarchicalmoving image decoding device 1 is defined to decode a processing targetsequence SEQ (hereinafter also referred to as a target sequence). Asillustrated in FIG. 3(a), the sequence SEQ includes a video parameterset VPS, a sequence parameter set SPS, a picture parameter set PPS,pictures PICT1 to PICTNP (where NP is a total number of picturesincluded in the sequence SEQ), and supplemental enhancement informationSEI.

In the video parameter set VPS, the number of layers included in thecoded data and a dependence relation between the layers are defined.

In the sequence parameter set SPS, a set of coding parameters referredto by the hierarchical moving image decoding device 1 is defined todecode the target sequence of the target layer. There may be theplurality of SPSs in the coded data. In this case, the SPS used for thedecoding for each target sequence of the target layer is selected from aplurality of candidates. The SPS used to decode a specific sequence isalso referred to as an active SPS. Hereinafter, the SPS means the activeSPS for the target sequence of the target layer, unless otherwisementioned.

In the picture parameter set PPS, a set of coding parameters referred toby the hierarchical moving image decoding device 1 is defined to decodeeach picture in the target sequence. There may be the plurality of PPSsin the coded data. In this case, one of the plurality of PPSs isselected from the pictures in the target sequence. The PPS used todecode a specific picture is also referred to as an active PPS.Hereinafter, the PPS means the active PPS for the target picture, unlessotherwise mentioned. The active SPS and the active PPS may be set to adifferent SPS or PPS for each layer.

(Picture Layer)

In the picture layer, a set of data referred to by the hierarchicalmoving image decoding device 1 is defined to decode the processingtarget picture PICT (hereafter also referred to as a target picture). Asillustrated in FIG. 3(b), the picture PICT includes slice headers SH1 toSHNS and a plurality of slices, that is, slices S1 to SNS (where NS is atotal number of slices included in the picture PICT).

In a case in which it is not necessary to distinguish the slice headersSH1 to SHNS or the slices S1 to SNS from each other, the slices aresometimes described below by omitting the subscripts of the codes. Thesame also applies to data which is data included in the hierarchicallycoded data DATA#C to be described below and is other data to whichsubscripts are appended.

A slice header SHk includes a coding parameter group referred to by thehierarchical moving image decoding device 1 to decide a method ofdecoding a corresponding slice Sk. For example, an SPS identifier(seq_parameter_set_id) designating the SPS or a PPS identifier(pic_parameter_set_id) designating the PPS are included. Further, slicetype designation information (slice_type) designating the type of sliceis an example of the coding parameter included in the slice header SH.

Examples of the types of slices which can be designated by the slicetype designation information include (1) an I slice using onlyintra-prediction at the time of coding, (2) a P slice usingunidirectional prediction or intra-prediction at the time of coding, and(3) a B slice using unidirectional prediction, bidirectional prediction,or intra-prediction at the time of coding can be exemplified.

(Slice Layer)

In the slice layer, a set of data referred to by the hierarchical movingimage decoding device 1 is defined to decode the processing target sliceS (also referred to as a target slice). As illustrated in FIG. 3(c), theslice S includes a sequence of coding tree blocks CTU1 to CTUNC (whereNC is a total number of CTUs included in the slice S).

(CTU Layer)

In the CTU layer, a set of data referred to by the hierarchical movingimage decoding device 1 is defined to decode the coding tree unit CTU(hereinafter also referred to as a target CTU) of the processing target.Further, the coding tree unit is also sometimes referred to as a codingtree block (CTB) or a largest cording unit (LCU).

The coding tree unit CTU includes a CTU header CTUH and pieces of codingunit information CU₁ to CU_(NL) (where NL is a total number of pieces ofcoding unit information included in the CTU). Here, a relation betweenthe coding tree unit CTU and the coding unit information CU will bedescribed as follows.

The coding tree unit CTU is split into units for specifying block sizesto perform the intra-prediction or the inter-prediction and each processfor transform.

The units of the coding tree unit CTU are split through recursivequadtree splitting. Hereinafter, a tree structure obtained through therecursive quadtree splitting is referred to as a coding tree.

Hereinafter, a unit corresponding to a leaf which is an end node of thecoding tree is referred as a coding node. Further, since the coding nodeis a basic unit of a coding process, the coding node is also referred toas a coding unit (CU).

That is, the coding unit information (hereinafter referred to as CUinformation) CU1 to CUNL is information corresponding to each codingnode (coding unit) obtained by performing the recursive quadtreesplitting on the coding tree unit CTU.

A root of a coding tree matches the coding tree unit CTU. In otherwords, the coding tree unit CTU matches a highest node of a treestructure of quadtree splitting that includes a plurality of codingnodes recursively.

Each coding node has a size of half of the horizontal and vertical sizesof a coding node (that is, a node located in the immediately higherlayer of the coding node) which is a master node of the coding node.

The size of the coding tree unit CTU and the size of each coding unitdepend on size designation information of the minimum coding nodeincluded in the sequence parameter set SPS and a difference in ahierarchy depth between the maximum coding node and the minimum codingnode. For example, in a case in which the size of the minimum codingnode is 8×8 pixels and the difference in the hierarchy depth between themaximum coding node and the minimum coding node is 3, the size of thecoding tree unit CTU is 64×64 pixels and the size of the coding node canbe any of four sizes, that is, 64×64 pixels, 32×32 pixels, 16×16 pixels,and 8×8 pixels.

(CTU Header)

The CTU header CTUH includes coding parameters referred to by thehierarchical moving image decoding device 1 to decide a method ofdecoding a target CTU. Specifically, as illustrated in FIG. 3(d), theCTU header CTUH includes a CTU splitting information SP_CTU designatinga splitting pattern of the target CTU into each CU, and a quantizationparameter difference Δqp (qp_delta) designating the magnitude of aquantization step.

The CTU splitting information SP_CTU is information indicating a codingtree for splitting the CTU and is specifically information fordesignating the shape, and the size of each CU included in the targetCTU and the position of each CU in the target CTU.

The CTU splitting information SP_CTU may not explicitly include theshape or the size of the CU. For example, the CTU splitting informationSP_CTU may be a set of flags indicating whether the entire target CTU ora partial region of the CTU is subjected to quad-splitting. In thiscase, the shape and the size of each CU can be specified by using theshape and the size of the CTU together.

(CU Layer)

In the CU layer, a set of data referred to by the hierarchical movingimage decoding device 1 is defined to decode a processing target CU(hereinafter also referred to as a target CU).

Here, a tree structure of data included in the CU will be describedbefore the specific contents of the data included in the CU informationCU is described. A coding node is a node of the roots of a predictiontree (PT) and a transform tree (TT). The prediction tree and thetransform tree will be described as follows.

In the prediction tree, the coding node is split into one predictionblock or a plurality of prediction blocks, and the position and size ofeach prediction block are defined. In other words, the prediction blockis one region or a plurality of non-overlapping regions included in thecoding node. The prediction tree includes one prediction block or aplurality of prediction block obtained through the above-describedsplitting.

A prediction process is performed for each prediction block.Hereinafter, the prediction block which is a unit of prediction is alsoreferred to as a prediction unit (PU).

Roughly speaking, the types of splitting (hereinafter abbreviated as PUsplitting) in the prediction tree are two types of a case ofintra-prediction and a case of inter-prediction.

In the case of the intra-prediction, as splitting methods, there are2N×2N (the same size as the coding node) and N×N. In the case of theinter-prediction, as splitting methods, there are 2N×2N (the same sizeas the coding node), 2N×N, 2N×nU, 2N×nD, N×2N, nL×2N, and nR×2N.

In the transform tree, the coding node is split into one transform blockor a plurality of transform blocks, and the position and size of eachtransform block are defined. In other words, the transform block is oneregion or a plurality of non-overlapping regions included in the codingnode. The transform tree includes one transform block or the pluralityof transform blocks obtained through the above-described splitting.

As the splitting of the transform tree, there are splitting in which aregion having the same size is allocated as the coding node as atransform block and splitting which is performed through the recursivequadtree splitting as in the splitting of the above-described treeblock.

A transform process is performed for each transform block. Hereinafter,the transform block which is a unit of transform is also referred to asa transform unit (TU).

(Data Structure of CU Information)

Subsequently, specific content of the data included in the CUinformation CU will be described with reference to FIG. 3(e). Asillustrated in FIG. 3(e), specifically, the CU information CU includes askip flag SKIP, prediction tree information (hereinafter abbreviated asPT information) PTI, and transform tree information (hereinafterabbreviated as TT information) TTI.

The skip flag SKIP is a flag that indicates whether a skip mode isapplied to the target PU. In a case in which the value of the skip flagSKIP is 1, that is, the skip mode is applied to the target CU, a part ofthe PT information PTI and the TT information TTI in the CU informationCU are omitted. The skip flag SKIP is omitted in the I slice.

[PT Information]

The PT information PTI is information regarding prediction tree(hereinafter abbreviated as a PT) included in the CU. In other words,the PT information PTI is a set of information regarding one PU or aplurality of PUs included in the PT and is referred to when a predictedimage is generated by the hierarchical moving image decoding device 1.As illustrated in FIG. 3(e), the PT information PTI includes predictiontype information PType and prediction information PInfo.

The prediction type information PType is information for designating amethod of generating a predicted image in regard to the target PU. Inthe base layer, the prediction type information PType is information fordesignating whether to use the intra-prediction or the inter-prediction.

The prediction information PInfo is prediction information used in theprediction method of designating the prediction type information PType.Intra-prediction information PP Intra is included in the case of theintra-prediction in the base layer. Further, in the case of theinter-prediction, inter-prediction information PP_Inter is included.

The inter-prediction information PP_Inter includes predictioninformation referred to when the hierarchical moving image decodingdevice 1 generates an inter-predicted image through theinter-prediction. More specifically, the inter-prediction informationPP_Inter includes inter-PU splitting information for designating asplitting pattern of the target CU into each inter-PU andinter-prediction parameters (motion compensation parameters) in regardto each inter-PU. The inter-prediction parameters include, for example,a merge flag (merge_flag), a merge index (merge_idx), an estimatedmotion vector index (mvp_idx), a reference picture index (ref_idx), aninter-prediction flag (inter_pred_flag), and a motion vector difference(mvd).

The intra-prediction information PP_Intra includes coding parametersreferred to when the hierarchical moving image decoding device 1generates an intra-predicted image through the intra-prediction. Morespecifically, the intra-prediction information PP_Intra includesintra-PU splitting information for designating a splitting pattern ofthe target CU into each intra-PU and intra-prediction parameters inregard to each intra-PU. The intra-prediction parameters are parametersfor designating an intra-prediction method (prediction mode) in regardto each intra-PU.

[TT Information]

The TT information TTI is information regarding the transform tree(hereinafter abbreviated as a TT) included in the CU. In other words,the TT information TTI is a set of information regarding one transformblock or a plurality of transform blocks included in the TT and isreferred to when the hierarchical moving image decoding device 1 decodesresidual data.

As illustrated in FIG. 3(e), the TT information TTI includes TTsplitting information SP_TT for designating a splitting pattern of thetarget CU into each transform block and quantization predictionresiduals QD1 o QDNT (where NT is a total number of blocks included inthe target CU).

Specifically, the TT splitting information SP_TT is information fordeciding the shape of each transform block included in the target CU andthe position of each transform block in the target CU. For example, theTT splitting information SP_TT can be realized by information(split_transform_unit_flag) indicating whether the splitting of thetarget node is performed and information (trafoDepth) indicating a depthof the splitting.

For example, when the size of the CU is 64×64, each transform blockobtained through the splitting can have a size from 32×32 pixels to 4×4pixels.

Each quantization prediction residual QD is coded data generated whenthe hierarchical moving image coding device 2 performs the followingprocesses 1 to 3 on a target block which is a processing targettransform block.

Process 1: A prediction residual obtained by subtracting a predictedimage from a coding target image is subjected to frequency transform(for example, discrete cosine transform (DCT), discrete sine transform(DST), or the like).

Process 2: A transform coefficient obtained in the process 1 isquantized.

Process 3: The transform coefficient quantized in the process 2 issubjected to variable-length coding.

The above-described quantization parameter qp indicates the magnitude ofa quantization step QP used when the hierarchical moving image codingdevice 2 quantizes the transform coefficient (QP=2qp/6).

(PU Splitting Information)

As the types of PU splitting designated based on the PU splittinginformation, there are the following total of eight kinds of patternswhen the size of the target CU is assumed to be 2N×2N pixels. That is,there are four symmetric splittings of 2N×2N pixels, 2N×N pixels, N×2Npixels, and N×N pixels and there are four asymmetric splittings of 2N×nUpixels, 2N×nD pixels, nL×2N pixels, and nR×2N pixels. Further, N=2m(where m is any integer equal to or greater than 1) is meant.Hereinafter, a prediction unit obtained by splitting the target CU isreferred to as a prediction block or a partition.

(Enhancement Layer)

For example, a data structure which is the substantially the same as thedata structure illustrated in FIG. 3 can also be adopted in regard tocoded data included in the layer notation of the enhancement layer(hereinafter referred to as enhancement layer coded data). However,additional information may be added or omitted or parameters may beomitted in regard to the enhancement layer coded data, as will bedescribed below.

In the slice layer, identification information (dependency_id,temporal_id, quality_id, and view_id) of layers of the spatialscalability, the temporal scalability, and the SNR scalability, and viewscalability may be coded.

The prediction type information PType included in the CU information CUis information for designating one of the intra-prediction, theinter-prediction, and the inter-layer image prediction as the method ofgenerating the predicted image in regard to the target CU. Theprediction type information PType includes a flag (inter-layer imageprediction flag) for designating whether to apply the inter-layer imageprediction mode. The inter-layer image prediction flag is also sometimesreferred to as texture_rl_flag, inter_layer_pred_flag, orbase_mode_flag.

In the enhancement layer, it may be designated whether the CU type ofthe target CU is the intra-CU, the inter-layer CU, the inter-CU, or theskip CU.

The intra-CU can be defined similarly with the intra-CU in the baselayer. In the intra-CU, the inter-layer image prediction flag is set to“0” and the prediction mode flag is set to “0”.

The inter-layer CU can be defined as the CU in which a decoded image ofa picture in the reference layer is used to generate a predicted image.In the inter-layer CU, the inter-layer image prediction flag is set to“1” and the prediction mode flag is set to “0”.

The skip CU can be defined similarly with the case of the HEVC schemedescribed above. For example, in the skip CU, the skip flag is set to“1”.

The inter-CU may be defined as the CU in which non-skip and motioncompensation (MC) is applied. In the inter-CU, for example, the skipflag is set to “0” and the prediction mode flag is set to “1”.

As described above, the coded data in the enhancement layer may begenerated according to a coding scheme different from the coding schemeof the lower layer. That is, the coding and decoding processes of theenhancement layer do not depend on kinds of codec of the lower layer.

The lower layer may be coded according to, for example, the MPEG-2 orH.264/AVC scheme.

In the enhancement layer coded data, the VPS may be enhanced and aparameter indicating a reference structure between layers may beincluded.

In the enhancement layer coded data, the SPS, the PPS, and the sliceheader may be enhanced. Information (for example, a syntax for directlyor indirectly deriving an inter-layer reference image set, aninter-layer reference image list, base control information, or the liketo be described below) related to the decoded image of the referencelayer used for inter-layer image prediction may be included.

The above-described parameters may be coded singly or the plurality ofparameters may be coded compositely. In a case in which the plurality ofparameters are coded compositely, indexes can be allocated tocombinations of the values of the parameters and the allocated indexesare coded. Since the parameters can be derived from other parameters orthe decoded information, the coding of the parameters can be omitted.

[Hierarchical Moving Image Decoding Device]

Hereinafter, the configuration of the hierarchical moving image decodingdevice 1 according to the embodiment will be described with reference toFIGS. 1 to 11.

(Configuration of Hierarchical Moving Image Decoding Device)

The schematic configuration of the hierarchical moving image decodingdevice 1 will be described as follows with reference to FIG. 4. FIG. 4is a functional block diagram illustrating the schematic configurationof the hierarchical moving image decoding device 1. The hierarchicalmoving image decoding device 1 decodes hierarchically coded data DATA (ahierarchically coded data DATAF supplied from the hierarchical movingimage coding device 2) to generate decoded image POUT#T of a targetlayer. Hereinafter, the target layer is assumed to be an enhancementlayer for which a base layer is a reference layer in the description.Therefore, the target layer is also a layer higher than the referencelayer. Conversely, the reference layer is a lower layer of the targetlayer.

As illustrated in FIG. 4, the hierarchical moving image decoding device1 includes an NAL demultiplexing section 11, a parameter set decodingsection 12, a tile setting section 13, a slice decoding section 14, abase decoding section 15, and a decoded picture management section 16.

The NAL demultiplexing section 11 demultiplexes the hierarchically codeddata DATA transmitted in a network abstraction layer (NAL) in a NALunit.

The NAL is a layer that is provided to abstract communication between avideo coding layer (VCL) and a lower system that transmits andaccumulates coded data.

The VCL is a layer in which a moving image coding process is performed.The coding is performed in the VCL. On the other hand, the lower systemmentioned herein corresponds to the file format of H.264/AVC and HEVC oran MPEG-2 system.

In the NAL, a bit stream generated in the VCL is partitioned in a unitreferred to as an NAL unit and is transmitted to a lower system which isa destination. The NAL unit includes coded data that is coded in the VCLand a header that is used to properly deliver the coded data to thelower system which is a destination. The coded data in each layer isstored in the NAL unit to be subjected to NAL multiplexing andtransmitted to the hierarchical moving image decoding device 1.

The hierarchically coded data DATA includes not only the NAL generatedby the VCL but also includes the NAL including parameter sets (VPS, SPS,and PPS) or an SEI. Such an NAL is referred to as a non-VCL NAL incontrast with the VCL NAL.

The NAL demultiplexing section 11 demultiplexes the hierarchically codeddata DATA to extract target layer coded data DATA#T and reference layercoded data DATA#$. The NAL demultiplexing section 11 supplies thenon-VCL NAL among the NALs included in the target layer coded dataDATA#T to the parameter set decoding section 12 and supplies the VCL NALto the slice decoding section 14.

The parameter set decoding section 12 decodes the parameter set, thatis, the VPS, the SPS, and the PPS, from the input non-VCL NAL andsupplies the parameter set to the tile setting section 13 and the slicedecoding section 14. The details of a process that has high relevancewith the present invention in the parameter set decoding section 12 willbe described.

The tile setting section 13 derives tile information regarding a picturebased on the input parameter set and supplies the tile information tothe slice decoding section 14. The tile information includes at leasttile splitting information of the picture.

The slice decoding section 14 generates the decoded picture or a partialregion of the decoded picture based on the input VCL NAL, parameter set,and tile information, and the reference picture and records the decodedpicture or the partial region of the decoded picture on a buffer insidethe decoded picture management section 16. The details of the slicedecoding section will be described below.

The decoded picture management section 16 records the input decodedpicture or base decoded picture on an internal decoded picture buffer(DPB) and performs generation of a reference picture list or decision ofan output picture. The decoded picture management section 16 outputs thedecoded picture recorded on the DPB as an output picture POUT#T at apredetermined timing to the outside.

The base decoding section 15 decodes the base decoded picture fromreference layer coded data DATA#R. The base decoded picture is a decodedpicture of a reference layer which is used at the time of decoding thedecoded picture of a target layer. The base decoding section 15 recordsthe decoded base decoded picture on the DPB inside the decoded picturemanagement section 16.

The detailed configuration of the base decoding section 15 will bedescribed with reference to FIG. 5. FIG. 5 is a functional block diagramexemplifying the configuration of the base decoding section 15.

As illustrated in FIG. 5, the base decoding section 15 includes a baseNAL demultiplexing section 151, a base parameter set decoding section152, a base tile setting section 153, a base slice decoding section 154,and a base decoded picture management section 156.

The base NAL demultiplexing section 151 demultiplexes the referencelayer coded data DATA#R, extracts the VCL NAL and the non-VCL NAL,supplies the non-VCL NAL to the base parameter set decoding section 152,and supplies the VCL NAL to the base slice decoding section 154.

The base parameter set decoding section 152 decodes the parameter set,that is, the VPS, the SPS, and the PPS, from the input non-VCL NAL andsupplies the parameter set to the base tile setting section 153 and thebase slice decoding section 154.

The base tile setting section 153 derives tile information regarding thepicture based on the input parameter set and supplies the tileinformation to the base slice decoding section 154.

The base slice decoding section 154 generates a decoded picture or apartial region of the decoded picture based on the input VCL NAL,parameter set, tile information, and reference picture and records thedecoded picture or the partial region of the decoded picture on a bufferinside the base decoded picture management section 156.

The base decoded picture management section 156 records the inputdecoded picture on the internal DPB and performs generation of thereference picture list and decision of an output picture. The basedecoded picture management section 156 outputs the decoded picturerecorded on the DPB as a base decoded picture at a predetermined timing.

(Parameter Set Decoding Section 12)

The parameter set decoding section 12 decodes the parameter set (theVPS, the SPS, and the PPS) used to decode the target layer from theinput coded data of the target layer and outputs the parameter set. Ingeneral, the parameter set is decoded based on a pre-decided syntaxtable. That is, a bit string is read from the coded data in a proceduredecided in the syntax table and a syntax value of a syntax componentincluded in the syntax table is decoded. A variable derived based on thedecoded syntax value may be included in a parameter set to be output, asnecessary. Accordingly, the parameter set output from the parameter setdecoding section 12 can be expressed as a set of the syntax value of thesyntax component related to the parameter set (the VPS, the SPS, and thePPS) included in the coded data and the variable derived from the syntaxvalue.

Hereinafter, a part of the syntax table related to picture informationand inter-layer position correspondence information and having highrelevance with the present invention in the syntax table used fordecoding in the parameter set decoding section 12 will be described indetail.

(Picture Information)

The parameter set decoding section 12 decodes picture information frominput target layer coded data. The picture information is schematicallyinformation for deciding the size of a decoded picture of a targetlayer. For example, the picture information includes informationindicating the width and height of the decoded picture of the targetlayer.

The picture information is included in, for example, the SPS. Thepicture information decoded from the SPS includes a width(pic_width_in_luma_samples) of the decoded picture and a height(pic_height_in_luma_samples) of the decoded picture. The value of syntaxpic_width_in_luma_samples corresponds to the width of the decodedpicture in a luminance pixel unit. The value of syntaxpic_height_in_luma_samples corresponds to the height of the decodedpicture in a luminance pixel unit.

The picture information is shared between layers. That is, the pictureinformation of a different layer from the target layer can be referredto at the time of decoding and coding the target layer.

(Picture Format Information)

The parameter set decoding section 12 decodes picture format informationfrom the input target layer coded data. The picture format informationincludes at least a color format identifier (chroma_format_idc) which isan identifier of the color format of the decoded picture. The pictureformat information is included in, for example, the SPS. In this case,the picture format of a specific picture is derived from the pictureformat information included in the SPS associated with the picture. Thepicture format information may be included in the VPS. In this case, thepicture format of the specific picture is derived from the pictureformat information associated in the VPS with the layer to which thepicture belongs.

The parameter set decoding section 12 derives a luminance pixel width(SubWidthC) per chroma pixel and a luminance pixel height (SubHeightC)per chroma pixel based on the value of the decoded color formatidentifier. The luminance pixel width (SubWidthC) per chroma pixel isthe same as a value obtained by subtracting the width of a pixel unit ofa chroma plane from the width of a pixel unit of a luminance plane, andSubWidthC is also referred to as a luminance chroma width ratio.Similarly, the luminance pixel width (SubHeightC) per chroma pixel isthe same as a value obtained by subtracting the height of a pixel unitof a chroma plane from the height of a pixel unit of a luminance plane,and SubHeightC is also referred to as a luminance chroma height ratio.The luminance chroma width ratio and the luminance color height ratioare collectively referred to as luminance chroma size ratios.

FIG. 6 is a table which is referred to by the parameter set decodingsection 12 and a table illustrating a relation among the color formatidentifier, the color format, the luminance chroma width ratio, and theluminance chroma height ratio. In FIG. 6, the parameter set decodingsection 12 derives a color format (Chroma format), the luminance chromawidth ratio (SubWidthC), and the luminance chroma height ratio(SubHeightC) from a color format identifier (chroma_format_idc).

(1) In a case in which the color format identifier is “0”, the colorformat of a picture is “monochrome” and values of SubWidthC andSubHeightC are each set to “1”. Here, “monochrome” means that a pictureis formed by only one image plane (for example, one luminance plane).

(2) In a case in which the color format identifier is “1”, the colorformat of a picture is “4:2:0”, the value of SubWidthC is set to “2” andthe value of SubHeightC is set to “2”. Here, in the color format of“4:2:0”, the picture is formed by one luminance plane and two chromaplanes. Additionally, the number of vertical pixels of the luminanceplane is twice the number of vertical pixels of the chroma plane, andthe number of horizontal pixels is likewise twice the number ofhorizontal pixels of the chroma plane.

(3) In a case in which the color format identifier is “2”, the colorformat of a picture is “4:2:2”, the value of SubWidthC is set to “2” andthe value of SubHeightC is set to “1”. Here, in the color format of“4:2:2”, the picture is formed by one luminance plane and two chromaplanes. Additionally, the number of vertical pixels of the luminanceplane is the same as the number of vertical pixels of the chroma plane,and the number of horizontal pixels of the luminance plane is twice thenumber of horizontal pixels of the chroma plane.

(4) In a case in which the color format identifier is “3”, the colorformat of a picture is “4:4:4”, the value of SubWidthC is set to “1” andthe value of SubHeightC is set to “1”. Here, in the color format of“4:4:4”, the picture is formed by one luminance plane and two chromaplanes. Additionally, the number of vertical pixels of the luminanceplane is the same as the number of vertical pixels of the chroma plane,and the number of horizontal pixels of the luminance plane is likewisethe same as the number of horizontal pixels of the chroma plane.

The process of deriving SubWidthC and SubHeightC in the foregoing (2),(3), and (4) can also be expressed collectively as follows. That is, ina case in which the color format identifier indicates a color format inwhich a picture is formed by one luminance plane and two chroma planes,the value of the luminance chroma width ratio (SubWidthC) is set to aratio of the number of horizontal pixels of the luminance plane to thenumber of horizontal pixels of the chroma plane and the value of theluminance chroma height ratio (SubHeightC) is set to a ratio of thenumber of vertical pixels of the luminance plane to the number ofvertical pixels of the chroma plane.

(Display Region Information)

The parameter set decoding section 12 decodes display region informationfrom the input target layer coded data. The display region informationis included in, for example, the SPS. The display region informationdecoded from the SPS includes a display region flag (conformance_flag).The display region flag indicates whether information indicating theposition of a display region (display region position information) isadditionally included in the SPS. That is, in a case in which thedisplay region flag is 1, the display region flag indicates that thedisplay region position information is additionally included. In a casein which the display region flag is 0, the display region flag indicatesthat the display region position information is not additionallyincluded.

In a case in which the display region flag is 1, the display regioninformation decoded from the SPS further includes a display region leftoffset (conf_win_left_offset), a display region right offset(conf_win_right_offset), a display region top offset(conf_win_top_offset), and a display region bottom offset(conf_win_bottom_offset) as display region position information.

In a case in which the display region flag is 0, an entire picture isset as a display region. Conversely, in a case in which the displayregion flag is 1, a partial region inside a picture indicated by thedisplay region position information is set. The display region is alsoreferred to as a conformance window.

A relation between the display region position information and thedisplay region will be described with reference to FIG. 7. FIG. 7 is adiagram exemplifying a relation between the display region which is apartial region in a picture and the display region position information.As illustrated, a display region is included in a picture, the displayregion top offset indicates a picture top side and a distance of thedisplay region top side, the display region left offset indicates apicture left side and a distance of the display region left side, thedisplay region right offset indicates a picture right side and adistance of the display region right side, and the display region bottomoffset indicates a picture bottom side and a distance of the displayregion bottom side. Accordingly, the position and size of the displayregion in the picture can be uniquely specified by the display regionposition information. The display region information may be anotherpiece of information by which the position and size of the displayregion in the picture can be uniquely specified.

(Inter-layer Position Correspondence Information)

The parameter set decoding section 12 decodes the inter-layer positioncorrespondence information from the input target layer coded data. Theinter-layer position correspondence information schematically indicatesa positional relation between correspondence regions of the target layerand the reference layer. For example, in which a case in which a certainobject (object A) is included in a picture of the target layer and apicture of the reference layer, a region corresponding to the object Aon the picture of the target layer and a region corresponding to theobject A on the picture of the reference layer are equivalent to thecorrespondence regions of the target layer and the reference layer. Theinter-layer position correspondence information may not necessarily beinformation accurately indicating a positional relation between thecorrespondence regions of the target layer and the reference layer. Ingenerally, the inter-layer position correspondence information indicatesan accurate positional relation between the correspondence regions ofthe target layer and the reference layer in order to improve accuracy ofinter-layer prediction.

(Inter-layer Position Correspondence Information: Scaled Reference LayerOffset)

The inter-layer position correspondence information includes informationthat defines a scaled reference layer offset. The plurality of scaledreference layer offsets can be included in the coded data. The scaledreference layer offsets are formed by four offsets corresponding toleft, top, right and bottom and are associated with a combination of twopictures, a target picture and a reference picture. In other words,information defining corresponding scaled reference layer offsets inregard to a combination of the target picture and a specific referencepicture is included in the inter-layer position correspondenceinformation. The information defining the reference layer offset may notnecessarily be included in all of the combinations of the targetpictures and reference pictures, but may be omitted in some of thecombinations under a specific condition and a default value can also beused.

The meanings of the offsets that form the scaled reference layer offsetswill be described with reference to FIG. 8. FIG. 8 is a diagramexemplifying a relation among the target layer picture, the referencelayer picture, and the inter-layer pixel correspondence offset.

FIG. 8(a) illustrates an example of a case in which an entire picture ofa reference layer corresponds to a part of a picture of a target layer.In this case, a region (target layer correspondence region) on thetarget layer corresponding to the entire picture of the reference layeris included inside the picture of the target layer. FIG. 8(b)illustrates an example of a case in which a part of the picture of thereference layer corresponds to the entire picture of the target layer.In this case, the picture of the target layer is included inside thecorrespondence region of the reference layer. The entire target layerpicture includes the offsets.

As illustrated in FIG. 8, a scaled reference layer left offset (an SRLleft offset in the drawing) indicates an offset of a reference layercorrespondence region left side with respect to the target layer pictureleft side. In a case in which the SRL left offset is greater than 0, itis indicated that the reference layer correspondence region left side islocated to the right of the target layer picture left side.

A scaled reference layer top offset (an SRL top offset in the drawing)indicates an offset of a reference layer correspondence region top sidewith respect to the target layer picture top side. In a case in whichthe SRL top offset is greater than 0, it is indicated that the referencelayer correspondence region top side is located to the bottom of thetarget layer picture top side.

A scaled reference layer right offset (an SRL right offset in thedrawing) indicates an offset of a reference layer correspondence regionright side with respect to the target layer picture right side. In acase in which the SRL right offset is greater than 0, it is indicatedthat the reference layer correspondence region right side is located tothe left of the target layer picture right side.

A scaled reference layer bottom offset (an SRL bottom offset in thedrawing) indicates an offset of a reference layer correspondence regionbottom side with respect to the target layer picture bottom side. In acase in which the SRL bottom offset is greater than 0, it is indicatedthat the reference layer correspondence region bottom side is located tothe top of the target layer picture bottom side.

Next, information defining the scaled reference layer offset(hereinafter referred to as scaled reference layer offset information),included in the coded data, and decoded by the parameter set decodingsection 12 will be described. For example, the scaled reference layeroffset information is included in an SPS extension (sps_estension) whichis a part of the SPS of a higher layer and is decoded according to thesyntax table illustrated in FIG. 9. FIG. 9 illustrates a part of thesyntax table which is referred to when the parameter set decodingsection 12 performs the SPS decoding and which is related to inter-layerpixel correspondence information.

The scaled reference layer offset information decoded from the SPSincludes a scaled reference layer offset number(num_scaled_ref_layer_offsets) included in the SPS extension.Additionally, the inter-layer pixel correspondence information includesthe number of scaled reference layer offsets indicated by the scaledreference layer offset number in conjunction with identifiers indicatingthe reference layer associated with the inter-layer pixel correspondenceoffsets. A scaled reference layer identifier (scaled_ref_layer_id) is anidentifier indicating a reference layer with which a subsequent scaledreference layer offset is associated. As the inter-layer pixelcorrespondence offsets, a scaled reference layer left offset(scaled_ref_layer_left_offset), a scaled reference layer top offset(scaled_ref_layer_top_offset), a scaled reference layer right offset(scaled_ref_layer_right_offset), and a scaled reference layer bottomoffset (scaled_ref_layer_bottom_offset) are included. Hereinafter,scaled_ref_layer_left_offset, scaled_ref_layer_top_offset,scaled_ref_layer_right_offset, and scaled_ref_layer_bottom_offset arecollectively referred to as a scaled reference layer offset syntax.

The parameter set decoding section 12 decodes the value of the scaledreference layer offset syntax by decoding codes of signed exponentialGolomb coding (se(v)) from the coded data. In the signed exponentialGolomb coding, specifically, default codes of the same names in HEVC canbe used. In the value of the decoded scaled reference layer offsetsyntax, a chroma pixel of a target picture is used as a unit. A relationof the following equation is established between an offset OY in aluminance pixel unit of the target picture and an offset OC in a chromapixel unit of the target picture.OY=RYC*OC

Here, RYC is a parameter indicating the number of luminance pixelscorresponding to one chroma pixel. In offsets (left and right offsets)in the horizontal direction, the luminance chroma width ratio(SubWidthC) in the target picture derived from the picture formatinformation can be used as a value of RYC. In offsets (top and rightoffsets) in the vertical direction, the luminance chroma height ratio(SubHightC) in the target picture can be used as a value of RYC.

In a case in which the scaled reference layer offset syntax is decodedin the chroma pixel unit and a case in which the color format of thetarget picture is 4:2:0 or 4:2:2, the value of the scaled referencelayer offset syntax can be decoded from a less code amount of codes thanin a case in which the scaled reference layer offset syntax is decodedin the luminance pixel unit. Conversely, in a case in which the colorformat of the target picture is 4:4:4, the scaled reference layer offsetsyntax can be decoded with higher precision, that is, luminanceone-pixel precision, than in a case in which the scaled reference layeroffset syntax is decoded in a luminance two-pixel unit.

(Inter-layer Position Correspondence Information: Reference LayerOffset)

The inter-layer position correspondence information includes informationdefining a reference layer offset (reference layer offset information).The plurality of reference layer offsets can be included in the codeddata. The reference layer offsets are formed by four offsetscorresponding to left, top, right and bottom and are associated with acombination of two pictures, a target picture and a reference picture.In other words, the corresponding reference layer offset can be includedin the inter-layer pixel correspondence information in each combinationof the target picture and a specific reference picture.

The reference layer left offset indicates an offset of a reference layerstandard region left side with respect to a reference layer picture leftside. When the offset value is greater than 0, it is indicated that thereference layer standard region left side is located to the right of areference layer picture left side.

The reference layer top offset indicates an offset of a reference layerstandard region top side with respect to a reference layer picture topside. When the offset value is greater than 0, it is indicated that thereference layer standard region top side is located to the bottom of areference layer picture top side.

The reference layer right offset indicates an offset of a referencelayer standard region right side with respect to a reference layerpicture right side. When the offset value is greater than 0, it isindicated that the reference layer standard region right side is locatedto the left of a reference layer picture right side.

The reference layer bottom offset indicates an offset of a referencelayer standard region bottom side with respect to a reference layerpicture bottom side. When the offset value is greater than 0, it isindicated that the reference layer standard region bottom side islocated to the top of a reference layer picture bottom side.

Next, a syntax corresponding to the reference layer offset informationand including a syntax corresponding to the reference layer offset willbe described. For example, the reference layer offset information isincluded in an SPS extension (sps_extension) which is a part of the SPSof a higher layer and is decoded according to the syntax tableillustrated in FIG. 10. FIG. 10 illustrates a part of the syntax tablewhich is referred to when the parameter set decoding section 12 performsthe SPS decoding and which is related to the reference layer offsetinformation.

The reference layer offset information decoded from the SPS includes areference layer offset number (num_ref_layer_offsets) included in theSPS extension. Additionally, the inter-layer pixel correspondenceinformation includes the number of reference layer offsets indicated bythe reference layer offset number in conjunction with identifiersindicating the reference layer associated with the reference layeroffsets. A reference layer identifier (ref_layer_id) is an identifierindicating a reference layer with which a subsequent reference layeroffset is associated. As the reference layer offsets, a reference layerleft offset (ref_layer_left_offset), a reference layer top offset(ref_layer_top_offset), a reference layer right offset(ref_layer_right_offset), and a reference layer bottom offset(ref_layer_bottom_offset) are included. Hereinafter,ref_layer_left_offset, ref_layer_top_offset, ref_layer_right_offset, andref_layer_bottom_offset are collectively referred to as a referencelayer offset syntax.

The parameter set decoding section 12 decodes the value of the referencelayer offset syntax by decoding codes of signed exponential Golombcoding (se(v)) from the coded data. In the value of the decodedreference layer offset syntax, a chroma pixel of a reference layerpicture associated via the reference layer offset syntax and thereference layer identifier is used as a unit. A relation of thefollowing equation is established between an offset ROY in a luminancepixel unit of the reference picture and an offset ROC in a chroma pixelunit of the reference picture.ROY=RRYC*ROC

Here, RRYC is a parameter indicating the number of luminance pixelscorresponding to one chroma pixel of an associated reference picture. Inoffsets (left and right offsets) in the horizontal direction, theluminance chroma width ratio (SubWidthC) in the associated referencepicture derived from the picture format information can be used as avalue of RRYC. In offsets (top and right offsets) in the verticaldirection, the luminance chroma height ratio (SubHightC) in the targetpicture can be used as a value of RRYC.

In a case in which the reference layer offset syntax is decoded in thechroma pixel unit and a case in which the color format of the referencepicture is 4:2:0 or 4:2:2, the value of the reference layer offsetsyntax can be decoded from a less code amount of codes than in a case inwhich the reference layer offset syntax is decoded in the luminancepixel unit. Conversely, in a case in which the color format of thereference picture is 4:4:4, the reference layer offset syntax can bedecoded with higher precision, that is, luminance one-pixel precision,than in a case in which the reference layer offset syntax is decoded ina luminance two-pixel unit.

As described above, the scaled reference layer offset information andthe reference layer offset information are included as the inter-layerpixel correspondence information. The unit of the syntax indicating eachoffset is set based on the target layer picture color format or thereference layer picture color format, as described above. Therefore, theunits of the syntax corresponding to the scaled reference layer offsetand the reference layer offset can be independently set in conformitywith the color formats of the target layer and the reference layer.

In the embodiment, the case in which both of the scaled reference layeroffset and the reference layer offset are transmitted has beendescribed. However, the advantageous effects of the present inventioncan be achieved even in a case in which only one of the scaled referencelayer offset and the reference layer offset is used, that is, a case inwhich only the syntax corresponding to one of the offsets is decodedfrom the coded data.

(Slice Decoding Section 14)

The slice decoding section 14 generates a decoded picture based on theinput VCL NAL, parameter set, and tile information and outputs thedecoded picture.

A schematic configuration of the slice decoding section 14 will bedescribed with reference to FIG. 11. FIG. 11 is a functional blockdiagram illustrating the schematic configuration of the slice decodingsection 14.

The slice decoding section 14 includes a slice header decoding section141, a slice position setting section 142, and a CTU decoding section144. The CTU decoding section 144 includes a prediction residualrestoration section 1441, a predicted image generation section 1442, anda CTU decoded image generation section 1443.

(Slice Header Decoding Section)

The slice header decoding section 141 decodes the slice header based onthe input VCL NAL and parameter set and outputs the slice header to theslice position setting section 142, a skip slice determination section143, and the CTU decoding section 144.

The slice header includes information (SH slice position information)regarding to a slice position in a picture and information (SH skipslice information) regarding a skip slice.

The slice header includes a in-picture head slice flag(first_slice_segment_in_pic_flag) as slice position information. In acase in which the in-picture head slice flag is 1, it is indicated thata target slice is located at the head in a picture in a decoding order.In a case in which the in-picture head slice flag is 0, it is indicatedthat a target slice is not located at the head in a picture in adecoding order.

The slice header includes slice PPS identifier(slice_pic_parameter_set_id) as slice position information. The slicePPS identifier is a PPS identifier associated with the target slice andtile information to be associated with the target slice is specified viathe PPS identifier.

(Slice Position Setting Section)

The slice position setting section 142 specifies a slice position in apicture based on the input slice header and tile information and outputsthe slice position to the CTU decoding section 144. The slice positionin the picture derived by the slice position setting section 142includes the position of each CTU included in the slice in the picture.

(CTU Decoding Section)

The CTU decoding section 144 schematically generates a decoded image ofa slice by decoding a decoded image of a region corresponding each CTUincluded in the slice based on input slice header, slice data, andparameter set. The decoded image of the slice is output as a part of thedecoded picture at a position indicated by an input slice position. Thedecoded image of the CTU is generated by the prediction residualrestoration section 1441, the predicted image generation section 1442,and the CTU decoded image generation section 1443 in the CTU decodingsection 144. The prediction residual restoration section 1441 decodesprediction residual information (TT information) included in the inputslice data to generate a prediction residual of a target CTU and outputsthe prediction residual. The predicted image generation section 1442generates a predicted image based on a prediction method and aprediction parameter indicated by prediction information (PTinformation) included in the input slice data and outputs the predictedimage. At this time, the coded data or the decoded image of thereference picture is used. The CTU decoded image generation section 1443generates a decoded image of the target CTU by adding the inputpredicted image and the prediction residual and outputs the decodedimage.

(Details of Predicted Image Generation Section)

The details of a predicted image generation process in a case in whichinter-layer image prediction is selected in a predicted image generationprocess by the above-described predicted image generation section 1442will be described.

A process of generating a prediction pixel value of a target pixelincluded in a target CTU to which the inter-layer image prediction isapplied is performed in the following procedure. First, a referencepicture position derivation process is performed to derive acorrespondence reference position. Here, the correspondence referenceposition is a position on the reference layer corresponding to a targetpixel (prediction target pixel) on a target layer picture. Moreprecisely, in a case in which a target of the predicted image generationprocess is luminance, the correspondence reference position is aposition of a reference layer picture on a luminance plane. In a case inwhich a target of the predicted image generation process is chroma, thecorrespondence reference position is a position of a reference layerpicture on a chroma plane. Since the pixels of the target layer and thereference layer do not necessarily have one-to-one correspondence, thecorrespondence reference position is expressed with precision less thana pixel unit in the reference layer. Next, by performing aninterpolation filter process using a derived correspondence referenceposition as an input, a prediction pixel value of a target pixel isgenerated.

In a correspondence reference position derivation process, acorrespondence reference position is derived based on inter-layer pixelcorrespondence information and the picture information included in theparameter set. A detailed procedure of the correspondence referenceposition derivation process will be described with reference to FIG. 1.Hereinafter, a target layer of the correspondence reference positionderivation process is assumed to be layer C (in which an index in theVPS of layer C is c) and a reference layer of the target layer isassumed to be layer R (in which an index in the VPS of layer R is r) inthe description. Here, a relation in which r is less c is establishedfrom two facts in which the reference layer of the target layer is alower layer than the target layer and a layer corresponding to a smallindex in the VPS is a lower which is further lower. FIG. 1 is aflowchart illustrating the correspondence reference position derivationprocess. The correspondence reference position derivation process in theinter-layer image prediction process between layer C and layer R in acase in which layer C is set as a target layer is performed in sequencein the order of the following S101 to S109.

(S101) It is determined whether a target of the predicted imagegeneration process is a luminance pixel or a chroma pixel. In a case inwhich the target is a luminance pixel, S102 is performed. In a case inwhich the target is a chroma pixel, S103 is performed.

(S102) A scaled reference layer offset is derived from the value of thescaled reference layer offset syntax corresponding to the referencelayer and decoded by the parameter set decoding section 12. Hereinafter,a scaled reference layer offset which is derived and related to areference layer (layer R) is referred to as SRLO[r]. Additionally, signsand scaled reference layer offsets corresponding to the left, top,right, and bottom and forming SRLO[r] are defined as follows.

Scaled reference layer left offset: SRLLO[r]

Scaled reference layer top offset: SRLTO[r]

Scaled reference layer right offset: SRLRO[r]

Scaled reference layer bottom offset: SRLBO[r]

The offsets SRLLO[r], SRLTO[r], SRLRO[r], and SRLBO[r] which formSRLO[r] are derived based on the value of the corresponding scaledreference layer offset syntax through the following calculation.SRLLO[r]=(scaled_ref_layer_left_offset[r]*SubWidthC)SRLTO[r]=(scaled_ref_layer_top_offset[r]*SubHeightC)SRLRO[r]=(scaled_ref_layer_right_offset[r]*SubWidthC)SRLBO[r]=(scaled_ref_layer_bottom_offset[r]*SubHeightC)

Here, SubWidthC and SubHeightC are variables that are derived from thepicture format information in the description of the parameter setdecoding section 12 and are a luminance chroma width ratio and aluminance chroma height ratio derived from the color format whichmatches the target layer.

A process of deriving the scaled reference layer offset can be expressedas follows. That is, in a case in which a target of the predicted imagegeneration process is a luminance pixel, the scaled reference layeroffset is derived by a product of the value of the scaled referencelayer offset syntax and the luminance chroma size ratio (the luminancechroma width ratio or the luminance chroma height ratio) in the targetlayer. Subsequently, S103 is performed.

(S103) The reference layer offsets on the reference layer (layer r) arederived. The reference layer offsets are formed by four offsetscorresponding to the left, top, right, and bottom (RLLO, RLTO, RLRO, andRLBO in order) and are derived based on the value of the reference layeroffset syntax by the following equations.RLLO=(ref_layer_left_offset[r]*RefSubWidthC)RLTO=(ref_layer_top_offset[r]*RefSubHeightC)RLRO=(ref_layer_right_offset[r]*RefSubWidthC)RLBO=(ref_layer_bottom_offset[r]*RefSubHeightC)

Here, RefSubWidthC and RefSubHeightC are variables that correspond tothe luminance chroma size ratios (SubWidthC and SubHeightC) derived fromthe picture format information in the description of the parameter setdecoding section 12 and are the luminance chroma size ratios derivedfrom the color format which matches the reference layer. That is, thevalue of SubWidthC derived based on the color format of the referencelayer is set in RefSubWidthC and the value of SubHeightC derived basedon the color format of the reference layer is set in RefSubHeightC.

A process of deriving the reference layer offsets can be expressed asfollows. That is, in a case in which a target of the predicted imagegeneration process is a luminance pixel, the reference layer offset isderived by a product by the value of the reference layer offset syntaxand the luminance chroma size ratio in the reference layer.Subsequently, S106 is performed.

(S104) Offsets SRLLO[r], SRLTO[r], SRLRO[r], and SRLBO[r] which formSRLO[j] described in S102 are derived based on the values of thecorresponding scaled reference layer offset syntax by the followingcalculation.SRLLO[r]=scaled_ref_layer_left_offset[r]SRLTO[r]=scaled_ref_layer_top_offset[r]SRLRO[r]=scaled_ref_layer_right_offset[r]SRLBO[r]=scaled_ref_layer_bottom_offset[r]

A process of deriving the scaled reference layer offsets can beexpressed as follows. That is, in a case in which a target of thepredicted image generation process is a chroma pixel, the value of thescaled reference layer offset syntax is derived as a scaled referencelayer offset.

Subsequently, S105 is performed.

(S105) The reference layer offsets (RLLO, RLTO, RLRO, and RLBO)described in S103 are derived by the following equations.RLLO=ref_layer_left_offset[r]RLTO=ref_layer_top_offset[r]RLRO=ref_layer_right_offset[r]RLBO=ref_layer_bottom_offset[r]

A process of deriving the reference layer offset can be expressed asfollows. That is, in a case in which a target of the predicted imagegeneration process is a chroma pixel, the value of the reference layeroffset syntax is derived as the value of the reference layer offset.Subsequently, S106 is performed.

(S106) The size of a scaled reference layer is derived based on thetarget layer picture size and the scaled reference layer offset derivedin S102 or S104. A width (SRLW) and a height (SRLH) of the scaledreference layer are derived based on a width (CL_PICW) and a height(CL_PICH) of the target layer picture by the following equations.SRLW=CL_PICW−(SRLLO+SRLRO)SRLH=CL_PICH−(SRLTO+SRLBO)

That is, according to the foregoing equations, the width of the scaledreference layer on the target layer is derived by subtracting a sum ofthe scaled reference layer left offset and the scaled reference layerright offset from the width of the target layer picture. The sameapplies to the height of the scaled reference layer on the target layer.Subsequently, S107 is performed. The reason why the sum of the offsetsis subtracted in the foregoing equations is that the sign of the offsetis defined so that the value of the offset is positive in a case inwhich the scaled reference layer (the reference layer correspondenceregion in the drawing) is inside the target layer picture, asillustrated in FIG. 8(a). In contrast, in a case in which the scaledreference layer is outside of the target layer picture and the signs ofthe offsets are defined so that the values of the offsets are positiveas in FIG. 8(b), the offsets are necessarily added, and thus the widthand height of the scaled reference layer are derived by the followingequations.SRLW=CL_PICW+(SRLLO+SRLRO)SRLH=CL_PICH+(SRLTO+SRLBO)

(S107) The size of a region serving as a scale calculation standard onthe reference layer (reference layer standard region) is derived basedon the size of the reference layer picture and the reference layeroffset derived in S103 or S105. A width (RLW) and a height (RLH) of thereference layer standard region are derived based on a width (RL_PICW)and a height (RL_PICH) of the reference layer picture by the followingequations.RLW=RL_PICW−(RLLO+RLRO)RLH=RL_PICH−(RLTO+RLBO)

That is, according to the foregoing equations, the width of thereference layer standard region is derived by subtracting a sum of thereference layer left offset and the reference layer right offset fromthe width of the reference layer picture. The same applies to the heightof the reference layer standard region. For the reference layer offset,the sign of the offset can be reversed as in the scaled reference layeroffset. In this case, a width (RLW) and a height (RLH) of the referencelayer standard region are respectively derived based on a width(RL_PICW) and a height (RL_PICH) of the reference layer picture by thefollowing equations.RLW=RL_PICW+(RLLO+RLRO)RLH=RL_PICH+(RLTO+RLBO)

Subsequently, S108 is performed.

(S108) Scales used for inter-layer prediction is derived based on thesize of the scaled reference layer derived in S106 and the size of thereference layer standard region derived in S107. A scale sx in thehorizontal direction and a scale sy in the vertical direction arerespectively derived by the following equations.sx=((RLW<<16)+(SRLW>>1))/SRLWsy=((RLH<<16)+(SRLH>>1))/SRLH

An operator “/” is an operator that represents division of an integer.

That is, according to the foregoing equations, values obtained bymultiplying the sizes of the reference layer reference regions by apredetermined constant (“<<16” in the foregoing equations) and dividingthe values by the sizes of the target layer reference regions. The term“(SRLW>>1)” is a term for adjusting rounding by division. Accordingly,when the effect of a unit or rounding adjustment is excluded, the scalecan be described as a ratio of the size (width or height) of thereference layer standard region to the size (width or height) of thescaled reference layer. Next, S109 is performed.

(S109) A reference pixel position with pixel precision of 1/16 isderived based on the scaled reference layer offsets derived in S102 orS104, the reference layer standard region offsets derived in S103 orS105, and the scales derived in S108. The values of a horizontalcomponent (x component) xRef16 and a vertical component (y component)yRef16 of the reference pixel position with pixel precision of 1/16 onthe reference layer correspond to a pixel position (xP, yP) on thetarget layer are respectively derived by the following equations.xRef16=(((xP−CL_OX)*sx+addX+(1<<11))>>12)+deltaX+RL_OXyRef16=(((yP−CL_OY)*sy+addY+(1<<11))>>12)+deltaY+RL_OY

whereCL_OX=SRLTOCL_OY=SRLTORL_OX=(RLLO<<4)RL_OY=(RLTO<<4)

Further, addX, addY, deltaX, and deltaY are parameters indicatingdeviation between a pixel on the target layer and a pixel on thereference layer which is caused by upsampling or interlacing.

That is, according to the foregoing equations, the reference pixelposition is calculated based on the scaled reference layer offsets, thereference layer standard region offsets, and the scales. Thecorrespondence reference position derivation process ends by setting thederived reference pixel position with pixel precision of 1/16 as thecorrespondence reference position.

The processes of (S101), (S102), and (S104) can be described in thefollowing equations using a ternary operator. Further, cIdx is anidentifier designating a plane in which a target of the predicted imagegeneration process forms a picture, cIdx=0 indicates a luminance plane,and cIdx=1 and 2 indicate a chroma plane.SRLLO[r]=cIdx==0?(scaled_ref_layer_left_offset[r]*SubWidthC):scaled_ref_layer_left_offset[r]SRLTO[r]=cIdx==0?(scaled_ref_layer_top_offset[r]*SubHeightC):scaled_ref_layer_top_offset [r]SRLRO[r]=cIdx==0?(scaled_ref_layer_right_offset[r]*SubWidthC):scaled_ref_layer_right_offset[r]SRLBO[r]=cIdx==0?(scaled_ref_layer_bottom_offset[r]*SubHeightC):scaled_ref_layer_bottom_offset[r]

The processes of (S101), (S103), and (S105) can also be described in thefollowing equations using a ternary operator.RLLO=cIdx==0?(ref_layer_left_offset[r]*RefSubWidthC):ref_layer_left_offset[r]RLTO=cIdx==0?(ref_layer_top_offset[r]*RefSubHeightC):ref_layer_top_offset[r]RLRO=cIdx==0?(ref_layer_right_offset[r]*RefSubWidthC):ref_layer_right_offset[r]RLBO=cIdx==0?(ref_layer_bottom_offset[r]*RefSubHeightC):ref_layer_bottom_offset[r]

In a case in which only the syntax corresponding to one offset of thescaled reference layer offset and the reference layer offset is decodedfrom coded data, a non-correspondence process is not performed (notincluded) in the correspondence reference position derivation process.

That is, in a case in which only the scaled reference layer offset isdecoded, the processes of S102 and S104 in regard to the scaledreference layer offsets are performed, but the processes of S103 andS105 in regard to the reference layer offsets are not included. Thewidth (RLW) and the height (RLH) of the reference layer standard regionin the process of S107 are respectively derived by the followingequations.RLW=RL_PICWRLH=RL_PICH

The reference pixel position with the pixel precision of 1/16 in theprocess of S109 is derived by the following equations.xRef16=(((xP−CL_OX)*sx+addX+(1<<11))>>12)+deltaXyRef16=(((yP−CL_OY)*sy+addY+(1<<11))>>12)+deltaY

In contrast, when only the reference layer offset is decoded, theprocesses of S103 and S105 in regard to the reference layer offsets areperformed, but the processes of S102 and S104 in regard to the scaledreference layer offsets are not included. Derivation is performed basedon the width (CL_PICW) and the height (CL_PICH) of the target layerpicture in the process of S106 by the following equations.SRLW=CL_PICWSRLH=CL_PICH

The reference pixel position with the pixel precision of 1/16 in theprocess of S109 is derived by the following equations.xRef16=((xP*sx+addX+(1<<11))>>12)+deltaX+RL_OXyRef16=((yP*sy+addY+(1<<11))>>12)+deltaY+RL_OY

In an interpolation filter process, a pixel value of a positioncorresponding to the correspondence reference position derived in thecorrespondence reference position derivation process is generated byapplying an interpolation filter to decoded pixels of pixels near thecorrespondence reference position on the reference layer picture.

(Advantageous Effects of Moving Image Decoding Device 1)

The hierarchical moving image decoding device 1 (hierarchical imagedecoding device) according to the above-described embodiment includesthe parameter set decoding section 12 that decodes the parameter set andthe predicted image generation section 1442 that generates a predictedimage through the inter-layer prediction with reference to the decodedpixels of the reference layer picture. The parameter set decodingsection 12 decodes the scaled reference layer offset coded in the chromapixel unit. The predicted image generation section 1442 derives thescaled reference layer offset by the product of the value of the scaledreference layer offset syntax and the luminance chroma size ratio of thetarget layer, calculates the scale based on the scaled reference layeroffset, derives the correspondence reference position with reference tothe scale, and performs the inter-layer prediction.

Accordingly, in a case in which the color format of the target pictureis 4:2:0 or 4:2:2, the hierarchical moving image decoding device 1 candecode the value of the reference layer offset syntax from a less codeamount of codes than in a case in which the reference layer offsetsyntax is decoded in the luminance pixel unit. Further, in a case inwhich the color format of the reference picture is 4:4:4, thehierarchical moving image decoding device 1 can decode the referencelayer offset syntax with higher precision, that is, luminance one-pixelprecision, than in a case in which the reference layer offset syntax isdecoded in a luminance two-pixel unit.

[Modification Example 1: Reference Layer Offset]

In a case in which the decoding of the reference layer offset syntaxwhich is decoded by the parameter set decoding section 12 is omitted inthe above-described hierarchical moving image decoding device 1, thereference layer offset derived based on the value of the reference layeroffset syntax in the predicted image generation section 1442 ispreferably matched to the scaled reference layer offset in considerationof the scale.

For example, in a case in which the decoding of the reference layeroffset syntax associated with the target layer C and the reference layerR is omitted, a default reference layer offset DEF_RLO is set to thereference layer offset in the predicted image generation section 1442.DEF_RLO is formed by DEF_RLLO, DEF_RLTO, DEF_RLRO, and DEF_RLBOcorresponding to left, top, right, and bottom offsets and arerespectively derived by the following equations.DEF_RLLO=−SRLLO*RL_PICW/CL_PICWDEF_RLTO=−SRLTO*RL_PICH/CL_PICHDEF_RLRO=−SRLRO*RL_PICW/CL_PICWDEF_RLBO=−SRLBO*RL_PICH/CL_PICH

That is, as the value of the reference layer offset, a value obtained byconverting the value of the corresponding scaled reference layer offsetbased on a ratio of size (width or height) between the reference layerpicture and the target layer picture is set. Here, the polarity(positive or negative sign) is reversed after multiplying the scaledreference layer offset by the reference layer picture and dividing thesize of the target layer picture. This is a case in which the positivedirections of the reference layer picture and the scaled reference layeroffset are defined to be opposite (for example, an outward direction ofthe scaled reference layer offset is positive and the inward directionof the reference layer picture is positive). In a case in which both ofthe offset syntaxes are set in the same direction, it is not necessaryto reverse the polarity, as will illustrated below.DEF_RLLO=SRLLO*RL_PICW/CL_PICWDEF_RLTO=SRLTO*RL_PICH/CL_PICHDEF_RLRO=SRLRO*RL_PICW/CL_PICWDEF_RLBO=SRLBO*RL_PICH/CL_PICH

In a case in which the size {the horizontal width, the vertical width}of the reference layer picture of the luminance component is {RL_PICW,RL_PICH} and the size of the target layer picture is {CL_PICW, CL_PICH},the size of the reference layer picture of the chroma component is

{RL_PICW/RefSubWidthC, RL_PICH/RefSubHeightC} and the size of the targetlayer picture is {CL_PICW/SubWidthC, CL_PICH/SubHeightC}. Therefore, ina case in which a target pixel is a chroma pixel, the value of thereference layer offset can be derived by the following equations.DEF_RLLO′=−SRLLO*(RL_PICW/RefSubWidthC)/(CL_PICW/SubWidthC)DEF_RLTO′=−SRLTO*(RL_PICH/RefSubHeightC)/(CL_PICH/SubHeightC)DEF_RLRO′=−SRLRO*(RL_PICW/RefSubWidthC)/(CL_PICW/SubWidthC)DEF_RLBO′=−SRLBO*(RL_PICH/RefSubHeightC)/(CL_PICH/SubHeightC)

“−” is a sign for correcting the direction of the offset syntax.

In a case in which the decoding of the reference layer offset syntaxassociated with the target layer C and the reference layer R is omitted,the reference layer offset syntax may be derived from the scaledreference layer offset syntax. Even in this case, as the value of thereference layer offset syntax, a value obtained by converting the valueof the corresponding scaled reference layer offset syntax based on aratio of size (width or height) between the reference layer picture andthe target layer picture is set.ref_layer_left_offset[r]=−scaled_ref_layer_left_offset[r]*RL_PICW/CL_PICWref_layer_top_offset[r]=−scaled_ref_layer_top_offset[r]*RL_PICH/CL_PICHref_layer_right_offset[r]=−scaled_ref_layer_right_offset[r]*RL_PICW/CL_PICWref_layer_bottom_offset[r]=−scaled_ref_layer_bottom_offset[r]*RL_PICH/CL_PICH

“−” is a sign for correcting the direction of the offset syntax.

The foregoing description can be applied directly to a case in which theluminance chroma size ratio {RefSubWidthC, RefSubHeightC} of thereference layer picture is the same as the luminance chroma size ratio{SubWidthC, SubHeightC} of the target layer picture.

In consideration of the luminance chroma size ratio, the reference layeroffset syntax may be derived by the following equations.ref_layer_left_offset[r]=−scaled_ref_layer_left_offset[r]*RL_PICW/CL_PICW*(SubWidthC/RefSubWidthC)ref_layer_top_offset[r]=−scaled_ref_layer_top_offset[r]*RL_PICH/CL_PICH*(SubHeightC/RefSubHeightC)ref_layer_right_offset[r]=−scaled_ref_layer_right_offset[r]*RL_PICW/CL_PICW*(SubWidthC/RefSubWidthC)ref_layer_bottom_offset[r]=−scaled_ref_layer_bottom_offset[r]*RL_PICH/CL_PICH*(SubHeightC/RefSubHeightC)

For example, in a case in which the reference layer offset syntax(ref_layer_left_offset[r], ref_layer_top_offset[r],ref_layer_right_offset[r],ref_layer_bottom_offset[r]) associated withthe target layer C and the reference layer R (layer index r) is omitted,0 may be set as each syntax value. In a case in which the target pixelis the luminance pixel in the correspondence reference positionderivation process in the predicted image generation section 1442,values of the reference layer offsets may be derived using the values ofDEF_RLO described above by the following equations.RLLO=(ref_layer_left_offset[r]*RefSubWidthC)+DEF_RLLORLTO=(ref_layer_top_offset[r]*RefSubHeightC)+DEF_RLTORLRO=(ref_layer_right_offset[r]*RefSubWidthC)+DEF_RLRORLBO=(ref_layer_bottom_offset[r]*RefSubHeightC)+DEF_RLBO

That is, the value of the reference layer offset is derived based on avalue obtained by adding the product of the value of the reference layeroffset syntax and the luminance chroma size ratio to the default value(DEF_RLO) of the reference layer offset. In a case in which the value ofthe reference layer offset syntax is omitted, the value of the productis 0. Therefore, a reference layer offset default value is set as thevalue of the reference layer offset.

In a case in which the target pixel is a chroma pixel, values of thereference layer offsets can be derived by the following equations.RLLO=ref_layer_left_offset[r]+DEF_RLLO′RLTO=ref_layer_top_offset[r]+DEF_RLTO′RLRO=ref_layer_right_offset[r]+DEF_RLRO′RLBO=ref_layer_bottom_offset[r]+DEF_RLBO′

That is, the values of the reference layer offsets are derived based onvalues obtained by adding the values of the reference layer offsetsyntax to the default values (DEF_RLO) of the reference layer offset.

According to the modification example, in a case in which the referencelayer offset syntax is omitted, the offset values corresponding to thescaled reference layer offsets are set in the reference layer offsets.Typically, an entire target layer picture and an entire reference layerpicture correspond to the physically same region in many cases.According to the foregoing method, the reference layer offset syntax canbe omitted in such typical cases. Accordingly, it is possible to decodethe reference layer offset from a small code amount of coded data.

[Modification Example 2: Scaled Reference Layer Offset]

In a case in which the decoding of the extention reference layer offsetsyntax which is decoded by the parameter set decoding section 12 isomitted in the above-described hierarchical moving image decoding device1, the scaled reference layer offset derived based on the value of thescaled reference layer offset syntax in the predicted image generationsection 1442 is preferably matched to the reference layer offset inconsideration of the scale.

For example, in a case in which the decoding of the scaled referencelayer offset syntax associated with the target layer C and the referencelayer R is omitted, a default scaled reference layer offset DEF_SRLO isset to the value of the scaled reference layer offset in the predictedimage generation section 1442. DEF_SRLO is formed by DEF_SRLLO,DEF_SRLTO, DEF_SRLRO, and DEF_SRLBO corresponding to left, top, right,and bottom offsets and are respectively derived by the followingequations.

For example, in a case in which the decoding of the scaled referencelayer offset syntax associated with the target layer C and the referencelayer R is omitted, a default scaled reference layer offset DEF_SRLO isset to the value of the scaled reference layer offset in the predictedimage generation section 1442. DEF_SRLO is formed by DEF_SRLLO,DEF_SRLTO, DEF_SRLRO, and DEF_SRLBO corresponding to left, top, right,and bottom offsets and are respectively derived by the followingequations.DEF_SRLLO=−RLLO*CL_PICW/RL_PICWDEF_SRLTO=−RLTO*CL_PICH/RL_PICHDEF_SRLRO=−RLRO*CL_PICW/RL_PICWDEF_SRLBO=−RLBO*CL_PICH/RL_PICH

That is, as the value of the scaled reference layer offset, a valueobtained by converting the value of the corresponding reference layeroffset based on a ratio of size (width or height) between the referencelayer picture and the target layer picture is set. Here, the polarity isreversed after multiplying the reference layer offset by the referencelayer picture and dividing the size of the target layer picture. This isa case in which the positive directions of the reference layer pictureand the reference layer offset are defined to be opposite (for example,an outward direction of the scaled reference layer offset is positiveand the inward direction of the reference layer picture is positive). Ina case in which both of the offset syntaxes are set in the samedirection, it is not necessary to reverse the polarity, as willillustrated below.DEF_SRLLO=−RLLO*CL_PICW/RL_PICWDEF_SRLTO=−RLTO*CL_PICH/RL_PICHDEF_SRLRO=−RLRO*CL_PICW/RL_PICWDEF_SRLBO=−RLBO*CL_PICH/RL_PICH

In a case in which the size {the horizontal width, the vertical width}of the reference layer picture of the luminance component is {RL_PICW,RL_PICH} and the size of the target layer picture is {CL_PICW, CL_PICH},the size of the chroma component of the reference layer picture is{RL_PICW/RefSubWidthC, RL_PICH/RefSubHeightC} and the size of the chromacomponent of the target layer picture is {CL_PICW/SubWidthC,CL_PICH/SubHeightC}. Therefore, in which a target pixel is a chromapixel, the value of the scaled reference layer offset can be derived bythe following equations.DEF_SRLLO′=−RLLO*(CL_PICW/SubWidthC)/(RL_PICW/RefSubWidthC)DEF_SRLTO′=−RLTO*(CL_PICW/SubHeightC)/(RL_PICW/RefSubHeightC)DEF_SRLRO′=−RLRO*(CL_PICW/SubWidthC)/(RL_PICW/RefSubWidthC)DEF_SRLBO′=−RLBO*(CL_PICW/SubHeightC)/(RL_PICW/RefSubHeightC)

“−” is a sign for correcting the direction of the offset syntax.

In a case in which the decoding of the scaled reference layer offsetsyntax associated with the target layer C and the reference layer R isomitted, the scaled reference layer offset syntax may be derived fromthe reference layer offset syntax. Even in this case, as the value ofthe reference layer offset syntax, a value obtained by converting thevalue of the corresponding reference layer offset syntax based on aratio of size (width or height) between the reference layer picture andthe target layer picture is set.scaled_ref_layer_left_offset[r]=−ref_layer_left_offset[r]*CL_PICW/RL_PICWscaled_ref_layer_top_offset[r]=−ref_layer_top_offset[r]*CL_PICH/RL_PICHscaled_ref_layer_right_offset[r]=−ref_layer_right_offset[r]*CL_PICW/RL_PICWscaled_ref_layer_bottom_offset[r]=−ref_layer_bottom_offset[r]*CL_PICH/RL_PICH

“−” is used to correct the direction of the offset syntax.

The foregoing description can be applied directly to a case in which theluminance chroma size ratio {RefSubWidthC, RefSubHeightC} of thereference layer picture is the same as the luminance chroma size ratio{SubWidthC, SubHeightC} of the target layer picture.

In consideration of the luminance chroma size ratio, the reference layeroffset syntax may be derived by the following equations.scaled_ref_layer_left_offset[r]=−ref_layer_left_offset[r]*CL_PICW/RL_PICW*(RefSubWidtchC/SubWidthC)scaled_ref_layer_top_offset[r]=−ref_layer_top_offset[r]*CL_PICH/RL_PICH*(RefSubHeightC/SubHeightC)scaled_ref_layer_right_offset[r]=−ref_layer_right_offset[r]*CL_PICW/RL_PICW*(RefSubWidthC/SubWidthC)scaled_ref_layer_bottom_offset[r]=−ref_layer_bottom_offset[r]*CL_PICH/RL_PICH*(RefSubHeightC/SubHeightC)

For example, in a case in which the scaled reference layer offset syntax(scaled_ref_layer_left_offset[r], scaled_ref_layer_top_offset[r],scaled_ref_layer_right_offset[r], scaled_ref_layer_bottom_offset[r])associated with the target layer C and the reference layer R (layerindex r) is omitted, 0 may be set as each syntax value. In a case inwhich the target pixel is the luminance pixel in the correspondencereference position derivation process in the predicted image generationsection 1442, values of the reference layer offsets may be derived usingthe values of DEF_SRRLO described above by the following equations.SRLLO=(scaled_ref_layer_left_offset[r]*RefSubWidthC)+DEF_SRLLOSRLTO=(scaled_ref_layer_top_offset[r]*RefSubHeightC)+DEF_SRLTOSRLRO=(scaled_ref_layer_right_offset[r]*RefSubWidthC)+DEF_SRLROSRLBO=(scaled_ref_layer_bottom_offset[r]*RefSubHeightC)+DEF_SRLBO

That is, the value of the reference layer offset is derived based on avalue obtained by adding the product of the value of the reference layeroffset syntax and the luminance chroma size ratio to the default value(DEF_RLO) of the reference layer offset. In a case in which the value ofthe reference layer offset syntax is omitted, the value of the productis 0. A reference layer offset default value is set as the value of thereference layer offset.

In a case in which the target pixel is a chroma pixel, values of thereference layer offsets can be derived by the following equations.SRLLO=scaled_ref_layer_left_offset[r]+DEF_SRLLO′SRLTO=scaled_ref_layer_top_offset[r]+DEF_SRLTO′SRLRO=scaled_ref_layer_right_offset[r]+DEF_SRLRO′SRLBO=scaled_ref_layer_bottom_offset[r]+DEF_SRLBO′

That is, the values of the scaled reference layer offsets are derivedbased on values obtained by adding the values of the scaled referencelayer offset syntax to the default values (DEF_SRLO) of the scaledreference layer offset.

According to the modification example, in a case in which the scaledreference layer offset syntax is omitted, the offset valuescorresponding to the reference layer offsets are set in the scaledreference layer offsets. Typically, an entire target layer picture andan entire reference layer picture correspond to the physically sameregion in many cases. According to the foregoing method, the scaledreference layer offset syntax can be omitted in such typical cases.Accordingly, it is possible to decode the scaled reference layer offsetfrom a small code amount of coded data.

[Modification Example 3: Transmission Position of Offsets]

The reference layer offset syntax or the scaled reference layer offsetsyntax which is decoded from the SPS extension (SPS) by the parameterset decoding section 12 in the above-described hierarchical moving imagedecoding device 1 has been described. The reference layer offset syntaxor the scaled reference layer offset syntax may be decoded from anotherparameter set or header. For example, the reference layer offset syntaxor the scaled reference layer offset syntax may be decoded from the VPS,the PPS, or the slice header. Specifically, in a case in which theoffsets are not changed for each picture, the VPS or the SPS may includean offset syntax. In a case in which the offsets are not changed foreach picture, the PPS or the slice header preferably include the offsetsyntax.

In a case in which the position of a region of interest on the side of atarget layer is moved in a picture unit, it is necessary to move atarget layer correspondence region on a corresponding reference layer.At this time, on the assumption that the reference layer correspondenceregion is moved by the scaled reference layer offsets as in FIG. 8(b)and the target layer correspondence region is moved in the referencelayer picture, the target layer correspondence region can also be moveddirectly in the reference layer picture based on the reference layeroffsets. That is, it is also possible to take one of a method of settingthe scaled reference layer offsets and a method of setting the referencelayer offsets. However, since the PPS or the slice header is frequentlycoded, overhead is considerable. Therefore, it is not desirable toinclude the offset syntax in the PPS or the slice header in regard toboth of the scaled reference layer offset and the reference layer offsetin order to move the position of the region of interest in the pictureunit since the code amount may increase.

Suitably, it is desirable not to change the reference layer offsets inthe picture unit by changing the scaled reference layer offsets in thepicture unit. Thus, it is possible to move the region of interest on thetarget layer in the picture unit and reduce the code amount of thereference layer offset information.

More specifically, the parameter set decoding section 12 preferably hasa configuration in which the scaled reference layer offset syntax isdecoded from at least one of the PPS and the slice header and thereference layer offset syntax is decoded from the VPS or the SPS.

(Configuration of Hierarchical Moving Image Coding Device)

A schematic configuration of the hierarchical moving image coding device2 will be described with reference to FIG. 12. FIG. 12 is a functionalblock diagram illustrating a schematic configuration of the hierarchicalmoving image coding device 2. The hierarchical moving image codingdevice 2 codes an input image PIN#T of a target layer with reference toreference layer coded data DATA#R to generate hierarchical coded dataDATA of the target layer. The reference layer coded data DATA#R isassumed to be coded in a hierarchical moving image coding devicecorresponding to a reference layer.

As illustrated in FIG. 12, the hierarchical moving image coding device 2includes an NAL multiplexing section 21, a parameter set coding section22, a tile setting section 23, a slice coding section 24, a decodedpicture management section 16, and a base decoding section 15.

The NAL multiplexing section 21 generates NAL-multiplexed hierarchicalmoving image coded data DATA by storing input target layer coded dataDATA#T and reference layer coded data DATA#R in an NAL unit and outputsthe NAL-multiplexed hierarchical moving image coded data DATA to theoutside.

The parameter set coding section 22 sets the parameter set (the VPS, theSPS, and the PPS) used to code an input image based on input tileinformation and the input image, packetizes the parameter set as a partof the target layer coded data DATA#T in the format of the VCL NAL, andsupplies the packetized parameter set to the NAL multiplexing section21.

The parameter set coded by the parameter set coding section 22 includesat least picture information, display region information, picture formatinformation, and inter-layer position correspondence information (scaledreference layer offset information and reference layer offsetinformation) described in relation to the hierarchical moving imagedecoding device 1. The parameter set coding section 22 codes a scaledreference layer offset syntax included in the scaled reference layeroffset information in a chroma pixel unit of the target layer. Thereference layer offset syntax included in the reference layer offsetinformation is coded in the chroma pixel unit of the reference layer.

The tile setting section 23 sets tile information of a picture based onthe input image and supplies the tile information to the parameter setcoding section 22 and the slice coding section 24. For example, the tileinformation indicating that a picture size is partitioned into M×N tilesis set. Here, M and N are any positive integer.

The slice coding section 24 codes a part of the input imagecorresponding to a slice that forms a picture based on the input image,parameter set, and tile information and the reference picture recordedin the decoded picture management section 16 to generate coded data ofthe part, and supplies the coded data as a part of the target layercoded data DATA#T to the NAL multiplexing section 21. The details of theslice coding section 24 will be described.

The decoded picture management section 16 is the same constituentelement as the decoded picture management section 16 included in theabove-described hierarchical moving image decoding device 1. Since it isnot necessary to output a picture recorded on an internal DPB of thedecoded picture management section 16 included in the hierarchicalmoving image coding device 2 as an output picture, the output can beomitted. In the description of the decoded picture management section 16of the hierarchical moving image decoding device 1, description made as“decoding” can be substituted with “coding” to be applied to the decodedpicture management section 16 of the hierarchical moving image codingdevice 2.

The base decoding section 15 is the same constituent element as the basedecoding section 15 included in the above-described hierarchical movingimage decoding device 1, and thus the detailed description will beomitted.

(Slice Coding Section)

Next, the details of the configuration of the slice coding section 24will be described with reference to FIG. 13. FIG. 13 is a functionalblock diagram illustrating a schematic configuration of the slice codingsection 24.

As illustrated in FIG. 13, the slice coding section 24 includes a sliceheader setting section 241, a slice position setting section 242, and aCTU coding section 244. The CTU coding section 244 contains a predictionresidual coding section 2441, a predicted image coding section 2442, anda CTU decoded image generation section 1443.

The slice header setting section 241 generates a slice header which isused to code the input image in a slice unit based on the inputparameter set and slice position information. The generated slice headeris output as a part of slice coded data and is supplied in conjunctionwith the input image to the CTU coding section 244.

The slice header generated by the slice header setting section 241includes at least SH slice position information.

The slice position setting section 242 decides a slice position in thepicture based on the input tile information and supplies the sliceposition to the slice header setting section 241.

The CTU coding section 244 codes the input image (target slice portion)in a CTU unit based on the input parameter set and slice header togenerate slice data and a decoded image (decoded picture) related to thetarget slice and outputs the slice data and the decoded image. Thecoding of the CTU is performed by the predicted image coding section2442, the prediction residual coding section 2441, and the CTU decodedimage generation section.

The predicted image coding section 2442 decides a prediction scheme anda prediction parameter of a target CTU included in the target slice,generates a predicted image based on the decided prediction scheme, andoutputs the predicted image to the prediction residual coding section2441 and the CTU decoded image generation section 1443. Informationregarding the prediction scheme or the prediction parameter is subjectedto variable-length coding as prediction information (PT information) andis output as a part of the slice data included in the slice coded data.The prediction scheme which can be selected by the predicted imagecoding section 2442 includes at least inter-layer image prediction.

In a case in which the inter-layer image prediction is selected as theprediction scheme, the predicted image coding section 2442 performs acorrespondence reference position derivation process, decides areference layer pixel position corresponding to a prediction targetpixel, and decides a prediction pixel value through an interpolationprocess based on the pixel position. As the correspondence referenceposition derivation process, each process described in the predictedimage generation section 1442 of the hierarchical moving image decodingdevice 1 can be applied. For example, a process of deriving thecorrespondence reference position based on the scaled reference layeroffset information and the reference layer offset information includedin the parameter set and described with reference to FIG. 1 is applied.

The prediction residual coding section 2441 outputs a quantizedtransform coefficient (TT information) obtained by performing transformand quantization on a difference image between the input image and thepredicted image as a part of the slice data included in the slice codeddata. A prediction residual is restored by applying inverse transformand inverse quantization on the quantized transform coefficient and therestored prediction residual is output to the CTU decoded imagegeneration section 1443.

The CTU decoded image generation section 1443 has the same function asthe constituent element having the same name of the hierarchical movingimage decoding device 1. Therefore, the same reference numeral is givenand the description thereof will be omitted.

(Advantageous Effects of Moving Image Coding Device 2)

The hierarchical moving image coding device 2 (hierarchical image codingdevice) according to the above-described embodiment includes theparameter set coding section 22 that codes the parameter set and thepredicted image coding section 2442 that generates a predicted imagethrough the inter-layer prediction with reference to the decoded pixelsof the reference layer picture. The parameter set coding section 22decodes the scaled reference layer offset coded in the chroma pixelunit. The predicted image coding section 2442 derives the scaledreference layer offset by the product of the value of the scaledreference layer offset syntax and the luminance chroma size ratio of thetarget layer, calculates the scale based on the scaled reference layeroffset, derives the correspondence reference position with reference tothe scale, and performs the inter-layer prediction.

Accordingly, in a case in which the color format of the target pictureis 4:2:0 or 4:2:2, the hierarchical moving image coding device 2 cancode the value of the reference layer offset syntax from a less codeamount of codes than in a case in which the reference layer offsetsyntax is coded in the luminance pixel unit. Further, in a case in whichthe color format of the reference picture is 4:4:4, the hierarchicalmoving image coding device 2 can code the reference layer offset syntaxwith higher precision, that is, luminance one-pixel precision, than in acase in which the reference layer offset syntax is coded in a luminancetwo-pixel unit.

(Examples of Application to Other Hierarchical Moving ImageCoding/Decoding Systems)

The above-described hierarchical moving image coding device 2 andhierarchical moving image decoding device 1 can be mounted on variousapparatuses transmitting, receiving, recording, and reproducing a movingimage for use. The moving image may be a natural moving image capturedby a camera or the like or may be an artificial moving image (includinga CG and a GUI) created by a computer or the like.

First, the above-described hierarchical moving image coding device 2 andhierarchical moving image decoding device 1 which can be used totransmit and receive a moving image will be described with reference toFIG. 14. FIG. 14(a) is a block diagram illustrating the configuration ofa transmission apparatus PROD_A on which the hierarchical moving imagecoding device 2 is mounted.

As illustrated in FIG. 14(a), a transmission apparatus PROD_A includes acoding section PROD_A1 that obtains coded data by coding a moving image,a modulation section PROD_A2 and that obtains a modulation signal bymodulating carrier waves using the coded data obtained by the codingsection PROD_A1, and a transmission section PROD_A3 that transmits themodulation signal obtained by the modulation section PROD_A2. Theabove-described hierarchical moving image coding device 2 is used as thecoding section PROD_A1.

The transmission apparatus PROD_A may further include a camera PROD_A4that captures a moving image as a supply source of a moving image inputto the coding section PROD_A1, a recording medium PROD_A5 that recordsthe moving image, an input terminal PROD_A6 that inputs the moving imagefrom the outside, and an image processing section A7 that generates orprocesses an image. In FIG. 14(a), the configuration of the transmissionapparatus PROD_A including all of the sections is exemplified, but someof the sections may be omitted.

The recording medium PROD_A5 may be a recording medium that records anuncoded moving image or may be a recording medium that records a movingimage coded according to a coding scheme for recording different from acoding scheme for transmission. In the latter case, a decoding section(not illustrated) that decodes coded data read from the recoding mediumPROD_A5 according to the coding scheme for recording may be interposedbetween the recording medium PROD_A5 and the coding section PROD_A1.

FIG. 14(b) is a block diagram illustrating a reception apparatus PROD_Bon which the hierarchical moving image decoding device 1 is mounted. Asillustrated in FIG. 14(b), the reception apparatus PROD_B includes areception section PROD_B1 that receives a modulated signal, ademodulation section PROD_B2 that obtains coded data by demodulating themodulated signal received by the reception section PROD_B1, and adecoding section PROD_B3 that obtains a moving image by decoding thecoded data obtained by the demodulation section PROD_B2. Theabove-described hierarchical moving image decoding device 1 is used asthe decoding section PROD_B3.

The reception apparatus PROD_B may further include a display PROD_B4that displays the moving image as a supply destination of the movingimage output by the decoding section PROD_B3 a recording medium PROD_B5that records the moving image, and an output terminal PROD_B6 thatoutputs the moving image to the outside. In FIG. 14(b), theconfiguration of the reception device PROD_B including all of thesesections is exemplified, but some of the sections may be omitted.

The recording medium PROD_B5 may be a recording medium that records anuncoded moving image or may be a recording medium that records a movingimage coded according to a coding scheme for recording different from acoding scheme for transmission. In the latter case, a coding section(not illustrated) that codes the moving image acquired from the decodingsection PROD_B3 according to the coding scheme for recording may beinterposed between the decoding section PROD_B3 and the recording mediumPROD_B5.

A transmission medium through which a modulated signal is transmittedmay be a wireless medium or a wired medium. A transmission form in whicha modulated signal is transmitted may be broadcasting (here, atransmission form in which a transmission designation is not specifiedin advance) or may be communication (here, a transmission form in whicha transmission destination is specified in advance). That is, thetransmission of the modulated signal may be realized by any one ofwireless broadcasting, wired broadcasting, wireless communication, andwired communication.

For example, a broadcast station (broadcast equipment or thelike)/reception station (a television receiver or the like) forterrestrial digital broadcasting is an example of the transmissionapparatus PROD_A/reception apparatus PROD _B transmitting or receiving amodulated signal by wireless broadcasting. Further, a broadcast station(broadcast equipment or the like)/reception station (television receiveror the like) for cable television broadcasting is an example of thetransmission apparatus PROD_A/reception apparatus PROD _B transmittingor receiving a modulated signal by wired broadcasting.

A server (a workstation or the like)/client (a television receiver, apersonal computer, a smartphone, or the like) for a video on demand(VOD) service in which the Internet is used, a moving image sharingservice, or the like is an example of the transmission apparatusPROD_A/reception apparatus PROD_B transmitting or receiving a modulatedsignal by communication (typically, one of wireless and wired media isused as a transmission medium in a LAN and a wired medium is used as atransmission medium in a WAN). Here, the personal computer includes adesktop PC, a laptop PC, and a tablet PC. The smartphone also includes amulti-function portable phone terminal.

The client for the moving image sharing service has not only a functionof decoding coded data downloaded from the server and displays the codeddata on a display but also a function of coding a moving image capturedby a camera and uploading the coded moving image to the server. That is,the client for the moving image sharing service functions as both of thetransmission apparatus PROD_A and the reception apparatus PROD_B.

The above-described hierarchical moving image coding device 2 andhierarchical moving image decoding device 1 which can be used to recordand reproduce a moving image will be described with reference to FIG.15. FIG. 15(a) is a block diagram illustrating the configuration of arecording apparatus PROD_C on which the above-described hierarchicalmoving image coding device 2 is mounted.

As illustrated in FIG. 15(a), the recording apparatus PROD_C includes acoding section PROD_C1 that obtains coded data by coding a moving imageand a writing section PROD_C2 that writes the coded data obtained by thecoding section PROD_C1 on a recording medium PROD_M. The above-describedhierarchical moving image coding device 2 is used as the coding sectionPROD_C1.

The recording medium PROD_M may be (1) a type of medium included in therecording apparatus PROD_C, such as a hard disk drive (HDD) or a solidstate drive (SSD), may be (2) a type of medium connected to therecording apparatus PROD_C, such as an SD memory card or a UniversalSerial Bus (USB) flash memory, or may be (3) a medium loaded on a drivedevice (not illustrated) included in the recording apparatus PROD_C,such as a Digital Versatile Disc (DVD) or a Blu-ray (registeredtrademark) disc (BD).

The recording apparatus PROD_C may further include a camera PROD_C3 thatcaptures a moving image as a supply source of a moving image to be inputto the coding section PROD_C1, an input terminal PROD_C4 that inputs amoving image from the outside, a reception section PROD_C5 that receivesa moving image, and an image processing section C6 that generates orprocesses an image. In FIG. 15(a), the configuration of the recordingapparatus PROD_C including all of the sections is exemplified, but someof the sections may be omitted.

The reception section PROD_C5 may be a reception section that receivesan uncoded moving image or may be a reception section that receivescoded data coded according to a coding scheme for transmission differentfrom a coding scheme for recording. In the latter case, a decodingsection (not illustrated) for transmission that decodes the coded datacoded according to the coding scheme for transmission may be interposedbetween the reception section PROD_C5 and the coding section PROD_C1.

Examples of the recording apparatus PROD_C include a DVD recorder, a BDrecorder, and a Hard Disk Drive (HDD) recorder (in this case, the inputterminal PROD_C4 or the reception PROD_C5 is a main supply source of amoving image). A camcorder (in this case, the camera PROD_C3 is a mainsupply source of a moving image), a personal computer (in this case, thereception section PROD_C5 or the image processing section C6 is a mainsupply source of a moving image), a smartphone (in this case, the cameraPROD_C3 or the reception section PROD_C5 serves a main supply source ofa moving image), and the like are also examples of the recordingapparatus PROD_C.

FIG. 15(b) is a block diagram illustrating the configuration of areproduction apparatus PROD_D on which the above-described hierarchicalmoving image decoding device 1 is mounted. As illustrated in FIG. 15(b),the reproduction apparatus PROD_D includes a reading section PROD_D1that reads coded data written on a recording medium PROD_M and adecoding section PROD_D2 that obtains a moving image by decoding thecoded data read by the reading section PROD_D1. The above-describedhierarchical moving image decoding device 1 is used as the decodingsection PROD_D2.

The recording medium PROD_M may be (1) a type of medium included in thereproduction apparatus PROD_D, such as an HDD or an SSD, may be (2) atype of medium connected to the reproduction apparatus PROD_D, such asan SD memory card or a USB flash memory, or may be (3) a medium loadedon a drive device (not illustrated) included in the reproductionapparatus PROD_D, such as a DVD or a BD.

The reproduction apparatus PROD_D may further include a display PROD_D3that displays a moving image as a supply destination of the moving imageoutput by the decoding section PROD_D2, an output terminal PROD_D4 thatoutputs the moving image to the outside, and a transmission sectionPROD_D5 that transmits the moving image. In FIG. 15(b), theconfiguration of the reproduction apparatus PROD_D including all of thesections is exemplified, but some of the sections may be omitted.

The transmission section PROD_D5 may be a transmission section thattransmits an uncoded moving image or may be a transmission section thattransmits the coded data coded according to a coding scheme fortransmission different from a coding scheme for recording. In the lattercase, a coding section (not illustrated) that codes a moving imageaccording to the coding scheme for transmission may be interposedbetween the decoding section PROD_D2 and the transmission sectionPROD_D5.

Examples of the reproduction apparatus PROD_D include a DVD player, a BDplayer, and an HDD player (in this case, the output terminal PROD_D4connected to a television receiver or the like is a main supplydestination of a moving image). A television receiver (in this case, thedisplay PROD_D3 is a main supply destination of a moving image), adigital signage (which is also referred to as an electronic signboard oran electronic bulletin board and the display PROD_D3 or the transmissionsection PROD_D5 is a main supply destination of a moving image), adesktop PC (in this case, the output terminal PROD_D4 or thetransmission section PROD_D5 is a main supply destination of a movingimage), a laptop or tablet PC (in this case, the display PROD_D3 or thetransmission section PROD_D5 is a main supply destination of a movingimage), a smartphone (in this case, the display PROD_D3 or thetransmission section PROD_D5 is a main supply destination of a movingimage), and the like are examples of the reproduction apparatus PROD_D.

(Hardware Realization and Software Realization)

Finally, blocks of the hierarchical moving image decoding device 1 andthe hierarchical moving image coding device 2 may be realized byhardware such as a logical circuit formed on an integrated circuit (ICchip) or may be realized by software using a central processing unit(CPU).

In the latter case, each of the foregoing devices includes a CPU thatexecutes a command of a control program realizing each function, aread-only memory (ROM) that stores the program, a random access memory(RAM) on which the program is loaded, and a storage device (recordingmedium) such as a memory that stores the program and various kinds ofdata. An object of the present invention can also be achieved byproviding each of the foregoing devices with a recording medium thatrecords a program code (an execution format program, an intermediatecode program, or a source program) of a control program of each of theforegoing devices which is software realizing the above-describedfunctions in a computer-readable manner and by causing a computer (a CPUor an MPU (Micro Processing Unit)) to read and execute the program coderecorded on the recording medium.

As the recording medium, for example, a kind of tape such as a magnetictape or a cassette tape, a kind of disc including a magnetic disk suchas floppy (registered trademark) disk/hard disk and an optical disc suchas Compact Disc Read-Only Memory (CD-ROM)/Magneto-Optical Disc (MOdiscs)/Mini Disc (MD)/Digital Versatile Disk (DVD)/CD Recordable (CD-R),a kind of card such as an IC card (including a memory card)/opticalcard, a kind of semiconductor memory such as mask ROM/ErasableProgrammable Read-Only Memory (EPROM)/Electrically Erasable andProgrammable Read-Only Memory (EEPROM) (registered trademark)/flash ROM,or a kind of logical circuit such as a Programmable Logic device (PLD)or a Field Programmable Gate Array (FPGA) can be used.

Each of the foregoing devices may be configured to be connected to acommunication network and the program code may be supplied via thecommunication network. The communication network may be able to transmitthe program code and is not particularly limited. For example, theInternet, an intra-net, an extra-net, a local area network (LAN), anintegrated services digital network (ISDN), a value-added network (VAN),a community antenna television (CATV) communication network, a virtualprivate network, a telephone circuit network, a mobile communicationnetwork, or a satellite communication network can be used. Atransmission medium that configures the communication network may be amedium capable of transmitting the program code and is not particularlylimited to a specific configuration or a kind of medium. For example, awired medium such as Institute of Electrical and Electronic Engineers(IEEE) 1394, a USB, power line broadcasting, a cable TV circuit line, atelephone line, or an asymmetric digital subscriber line (ADSL) circuit,an infrared medium such as infrared data association (IrDA) or a remotecontroller, or a wireless medium such as Bluetooth (registeredtrademark), IEEE 802.11 wireless, high data rate (HDR), near fieldcommunication (NFC), digital living network alliance (DLNA), a portabletelephone network, a satellite circuit, or a terrestrial digital networkcan be used. The present invention can also be realized in a form of acomputer data signal in which the program code is embodied throughelectronic transmission and is embedded in a carrier wave.

The present invention is not limited to the above-described embodiments,but may be modified in various forms within the scope indicated by theclaims. Embodiments obtained by properly combining technical meansdisclosed in different embodiments are also included in the technicalscope of the present invention.

[Supplements]

The present invention can be expressed as follows.

In order to resolve the foregoing problems, an image decoding deviceaccording to the present invention decodes coded data that ishierarchically coded to restore a decoded picture of a higher layerwhich is a target layer. The image decoding device includes: a parameterset decoding section that decodes a parameter set; and a predicted imagegeneration section that generates a predicted image by inter-layerprediction with reference to decoded pixels of a reference layerpicture. The parameter set decoding section decodes a color format of atarget layer picture and derives a luminance chroma size ratio of atarget layer picture based on the color format. The parameter setdecoding section decodes a scaled reference layer offset syntax which iscoded in a chroma pixel unit of the target layer. The predicted imagegeneration section derives a scaled reference layer offset by a productof a value of the scaled reference layer offset syntax and the luminancechroma size ratio of the target layer picture, calculates a scale basedon the scaled reference layer offset, derives a correspondence referenceposition with reference to the scale, and performs the inter-layerprediction.

In the image decoding device, the parameter set decoding section maydecode a color format of the reference layer picture and derive aluminance chroma size ratio of the reference layer picture based on thecolor format. The parameter set decoding section may decode a referencelayer offset syntax coded in a chroma pixel unit of a reference layer.The predicted image generation section may derive a reference layeroffset by a product of a value of the reference layer offset syntax anda luminance chroma size ratio of the reference layer picture, calculatea scale based on the reference layer offset, derive a correspondencereference position with reference to the scale, and perform theinter-layer prediction.

In the image decoding device, the predicted image generation section mayset the product of the scaled reference layer offset syntax and theluminance chroma size ratio of the target layer picture as the scaledreference layer offset in a case in which a target of a predicted imagegeneration process is a luminance pixel, and may set the value of thescaled reference layer offset syntax as the scaled reference layeroffset in a case in which the target of the predicted image generationprocess is a chroma pixel.

In the image decoding device, the predicted image generation section mayset the product of the reference layer offset syntax and the luminancechroma size ratio of the reference layer picture as the reference layeroffset in a case in which a target of a predicted image generationprocess is a luminance pixel, and may set the value of the referencelayer offset syntax as the reference layer offset in a case in which thetarget of the predicted image generation process is a chroma pixel.

In the image decoding device, in a case in which the parameter setdecoding section omits to decode the reference layer offset syntax, thepredicted image generation section may set a value obtained byconverting a value of the scaled reference layer offset based on a ratiobetween sizes of the target layer picture and the reference layerpicture as the value of the reference layer offset.

In the image decoding device, the parameter set decoding section maydecode the scaled reference layer offset syntax from either a PPS or aslice header and decode the reference layer offset syntax from a VPS oran SPS.

In order to resolve the foregoing problems, an image coding deviceaccording to the present invention generates coded data of a higherlayer which is a target layer from an input image. The image codingdevice includes: a parameter set coding section that codes a parameterset; and a predicted image generation section that generates a predictedimage by inter-layer prediction with reference to decoded pixels of areference layer picture. The parameter set coding section codes a colorformat of a target layer picture and derives a luminance chroma sizeratio of the target layer picture based on the color format. Theparameter set coding section codes a scaled reference layer offsetsyntax in a chroma pixel unit of the target layer. The predicted imagegeneration section derives a scaled reference layer offset by a productof a value of the scaled reference layer offset syntax and the luminancechroma size ratio of the target layer picture, calculates a scale basedon the scaled reference layer offset, derives a correspondence referenceposition with reference to the scale, and performs the inter-layerprediction.

INDUSTRIAL APPLICABILITY

The present invention can be applied to a hierarchical image decodingdevice that decodes coded data in which image data is hierarchicallycoded and a hierarchical image coding device that generates the codeddata in which the image data is hierarchically coded. The presentinvention can also be applied to a data structure of hierarchicallycoded data which is generated by the hierarchical image coding deviceand is referred to by the hierarchical image decoding device.

REFERENCE SIGNS LIST

1 hierarchical moving image decoding device (image decoding device)

11 NAL demultiplexing section

12 parameter set decoding section

13 tile setting section

14 slice decoding section

141 slice header decoding section

142 Slice position setting section

144 CTU decoding section

1441 prediction residual restoration section

1442 predicted image generation section

1443 CTU decoded image generation section

15 base decoding section

151 base NAL demultiplexing section

152 base parameter set decoding section

153 base tile setting section

154 base slice decoding section

156 base decoded picture management section

16 decoded picture management section

2 hierarchical moving image coding device (image coding device)

21 NAL multiplexing section

22 parameter set coding section

23 tile setting section

24 slice coding section

241 slice header setting section

242 slice position setting section

244 CTU coding section

2441 prediction residual coding section

2442 predicted image coding section (predicted image generation section)

The invention claimed is:
 1. An image decoding device that decodes codeddata that is hierarchically coded to reconstruct a decoded picture of ahigher layer which is a target layer, the image decoding devicecomprising: a parameter set decoding circuit that decodes a parameterset; and a predicted image generation circuit that generates a predictedimage by inter-layer prediction with reference to decoded pixels of areference layer picture, wherein the parameter set decoding circuitdecodes a color format identifier and derives a luma chroma width ratiodepending upon a chroma format, which is specified by the color formatidentifier, wherein the parameter set decoding circuit decodes: (i) ascaled reference layer offset syntax which is decoded in a chroma pixelunit of the target layer picture, and (ii) a reference layer offsetsyntax which is decoded in a chroma pixel unit of the reference layerpicture, wherein the scaled reference layer offset syntax specifies anoffset between a top-left sample of a reference region in the targetlayer picture and a top-left sample of the target layer picture, and thereference layer offset syntax specifies an offset between a top-leftsample of the reference region in the reference layer picture and atop-left sample of the reference layer picture, wherein the predictedimage generation circuit derives a reference position by using a scaledreference layer offset, a reference layer offset, and a scale, whereinthe scaled reference layer offset is derived by multiplying a value ofthe scaled reference layer offset syntax by a first luma chroma widthratio that is set to the luma chroma width ratio of the target layerpicture, wherein the reference layer offset is derived by multiplying avalue of the reference layer offset syntax by a second luma chroma widthratio that is set to the luma chroma width ratio of the reference layerpicture, and wherein the scale is derived by using the scaled referencelayer offset and the reference layer offset.
 2. An image coding devicethat generates coded data of a higher layer which is a target layer froman input image, the image coding device comprising: a parameter setcoding circuit that codes a parameter set; and a predicted imagegeneration circuit that generates a predicted image by inter-layerprediction with reference to decoded pixels of a reference layerpicture, wherein the parameter set coding circuit codes a color formatidentifier and derives a luma chroma width ratio depending upon a chromaformat, which is specified by the color format identifier, wherein theparameter set coding circuit codes a scaled reference layer offsetsyntax which is coded in a chroma pixel unit of the target layer pictureand a reference layer offset syntax which is coded in a chroma pixelunit of the reference layer picture, wherein the scaled reference layeroffset syntax specifies an offset between a top-left sample of areference region in the target layer picture and a top-left sample ofthe target layer picture, and the reference layer offset syntaxspecifies an offset between a top-left sample of the reference region inthe reference layer picture and a top-left sample of the reference layerpicture, wherein the predicted image generation circuit derives areference position by using a scaled reference layer offset, a referencelayer offset, and a scale, wherein the scaled reference layer offset isderived by multiplying a value of the scaled reference layer offsetsyntax by a first luma chroma width ratio that is set to the luma chromawidth ratio of the target layer picture, wherein the reference layeroffset is derived by multiplying a value of the reference layer offsetsyntax by a second luma chroma width ratio that is set to the lumachroma width ratio of the reference layer picture, and wherein the scaleis derived by using the scaled reference layer offset and the referencelayer offset.
 3. An image decoding method for decoding coded data thatis hierarchically coded to reconstruct a decoded picture of a higherlayer which is a target layer, the image decoding method comprising:decoding a color format identifier; deriving a luma chroma width ratiodepending upon a chroma format, which is specified by the color formatidentifier; decoding a scaled reference layer offset syntax which isdecoded in a chroma pixel unit of the target layer picture and areference layer offset syntax which is decoded in a chroma pixel unit ofa reference layer picture; wherein the scaled reference layer offsetsyntax specifies an offset between a top-left sample of a referenceregion in the target layer picture and a top-left sample of the targetlayer picture, and the reference layer offset syntax specifies an offsetbetween a top-left sample of the reference region in the reference layerpicture and a top-left sample of the reference layer picture; deriving ascaled reference layer offset by multiplying a value of the scaledreference layer offset syntax by a first luma chroma width ratio that isset to the luma chroma width ratio of the target layer picture; derivinga reference layer offset by multiplying a value of the reference layeroffset syntax by a second luma chroma width ratio that is set to theluma chroma width ratio of the reference layer picture, deriving a scaleby using the scaled reference layer offset and the reference layeroffset; deriving a reference position by using the scaled referencelayer offset, the reference layer offset, and the scale; and generatinga predicted image by inter-layer prediction.
 4. An image coding methodfor generating coded data of a higher layer which is a target layer froman input image, the image coding method comprising: coding a colorformat identifier; deriving a luma chroma width ratio depending on achroma format, which is specified by the color format identifier; codinga scaled reference layer offset syntax which is coded in a chroma pixelunit of the target layer picture and a reference layer offset syntaxwhich is coded in a chroma pixel unit of the reference layer picture;wherein the scaled reference layer offset syntax specifies an offsetbetween a top-left sample of a reference region in the target layerpicture and a top-left sample of the target layer picture, and thereference layer offset syntax specifies an offset between a top-leftsample of the reference region in the reference layer picture and atop-left sample of the reference layer picture; deriving a scaledreference layer offset by multiplying a value of the scaled referencelayer offset syntax by a first luma chroma width ratio that is set tothe luma chroma width ratio of the target layer picture; deriving areference layer offset by multiplying a value of the reference layeroffset syntax by a second luma chroma width ratio that is set to theluma chroma width ratio of the reference layer picture; deriving a scaleby using the scaled reference layer offset and the reference layeroffset; deriving a reference position by using the scaled referencelayer offset, the reference layer offset, and the scale; and generatinga predicted image by inter-layer prediction.
 5. A non-transitorycomputer-readable recoding medium storing a program for making acomputer decode coded data that is hierarchically coded to reconstruct adecoded picture of a higher layer which is a target layer, wherein theprogram making the computer: decode a color format identifier; derive aluma chroma width ratio depending upon a chroma format, which isspecified by the color format identifier; decode a scaled referencelayer offset syntax which is decoded in a chroma pixel unit of thetarget layer picture and a reference layer offset syntax which isdecoded in a chroma pixel unit of a reference layer picture; wherein thescaled reference layer offset syntax specifies an offset between atop-left sample of a reference region in the target layer picture and atop-left sample of the target layer picture, and the reference layeroffset syntax specifies an offset between a top-left sample of thereference region in the reference layer picture and a top-left sample ofthe reference layer picture; derive a scaled reference layer offset bymultiplying a value of the scaled reference layer offset syntax by afirst luma chroma width ratio that is set to the luma chroma width ratioof the target layer picture; derive a reference layer offset bymultiplying a value of the reference layer offset syntax by a secondluma chroma width ratio that is set to the luma chroma width ratio ofthe reference layer picture, derive a scale by using the scaledreference layer offset and the reference layer offset; derive areference position by using the scaled reference layer offset, thereference layer offset, and the scale; and generate a predicted image byinter-layer prediction.
 6. A non-transitory computer-readable recodingmedium storing a program for making a computer generate coded data of ahigher layer which is a target layer from an input image, wherein theprogram making the computer: code a color format identifier; derive lumachroma width ratio depending on a chroma format, which is specified bythe color format identifier; code a scaled reference layer offset syntaxwhich is coded in a chroma pixel unit of the target layer picture and areference layer offset syntax which is coded in a chroma pixel unit ofthe reference layer picture; wherein the scaled reference layer offsetsyntax specifies an offset between a top-left sample of a referenceregion in the target layer picture and a top-left sample of the targetlayer picture, and the reference layer offset syntax specifies an offsetbetween a top-left sample of the reference region in the reference layerpicture and a top-left sample of the reference layer picture; derive ascaled reference layer offset by multiplying value of the scaledreference layer offset syntax by a first luma chroma width ratio that isset to the luma chroma size ratio of the target layer picture; derive areference layer offset by multiplying a value of the reference layeroffset syntax by a second luma chroma width ratio that is set to theluma chroma width ratio of the reference layer picture; derive a scaleby using the scaled reference layer offset and the reference layeroffset; derive a reference position by using the scaled reference layeroffset, the reference layer offset, and the scale; and generate apredicted image by inter-layer prediction.